Initialize gradle project

22 files changed, 0 insertions, 3193 deletions

diff --git a/src/pl/edu/mimuw/cloudatlas/model/Attribute.java b/src/pl/edu/mimuw/cloudatlas/model/Attribute.java
deleted file mode 100644
index 46ffab3..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/Attribute.java
+++ /dev/null
@@ -1,106 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-/**
- * Represents an attribute (without value, name only).
- * <p>
- * A valid attribute name is an identifier starting with a letter and containing only letters and digits. It can
- * additionally start with an ampersand - such names are reserved for queries.
- * <p>
- * This class is immutable.
- */
-public class Attribute {
-    private final String name;
-
-    /**
-     * Creates a new <code>Attribute</code> object with the specified <code>name</code>.
-     *
-     * @param name the name of the attribute
-     * @throws IllegalArgumentException if the <code>name</code> does not meet the rules
-     */
-    public Attribute(String name) {
-        if(!name.matches("^&?[a-zA-Z]{1}[a-zA-z0-9_]*$"))
-            throw new IllegalArgumentException("Invalid name: may contain only letters, digits, underscores, "
-                    + "must start with a letter and may optionally have an ampersand at the beginning.");
-        this.name = name;
-    }
-
-    /**
-     * Indicates whether an <code>attribute</code> represents a query. This is true if and only if the attribute's name starts with an ampersand.
-     *
-     * @param attribute the attribute to check
-     * @return whether the <code>attribute</code> represents a query
-     */
-    public static boolean isQuery(Attribute attribute) {
-        return attribute.getName().startsWith("&");
-    }
-
-    /**
-     * Gets the name of this attribute.
-     *
-     * @return string representing name
-     */
-    public String getName() {
-        return name;
-    }
-
-    /**
-     * Returns a hash code value for this attribute. For proper behavior when using <code>Attribute</code> objects in
-     * <code>HashMap</code>, <code>HashSet</code> etc. this is the hash code of a string representing the attribute's name.
-     *
-     * @return hash code for this attribute
-     */
-    @Override
-    public int hashCode() {
-        return name.hashCode();
-    }
-
-    /**
-     * Indicates whether another object is equal to this attribute.
-     *
-     * @param object the object to check
-     * @return true if and only if the <code>object</code> is an instance of <code>Attribute</code> class and has
-     * an identical name
-     */
-    @Override
-    public boolean equals(Object object) {
-        if(object == null)
-            return false;
-        if(getClass() != object.getClass())
-            return false;
-        return name.equals(((Attribute)object).name);
-    }
-
-    /**
-     * Returns a textual representation of this attribute.
-     *
-     * @return the name of this attribute
-     */
-    @Override
-    public String toString() {
-        return name;
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/AttributesMap.java b/src/pl/edu/mimuw/cloudatlas/model/AttributesMap.java
deleted file mode 100644
index 4065ad6..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/AttributesMap.java
+++ /dev/null
@@ -1,282 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import java.util.HashMap;
-import java.util.Iterator;
-import java.util.Map;
-import java.util.Map.Entry;
-
-/**
- * Represents a map from <code>Attribute</code> to <code>Value</code>. It cannot contain duplicate keys.
- */
-public class AttributesMap implements Iterable<Entry<Attribute, Value>>, Cloneable {
-    private Map<Attribute, Value> map = new HashMap<Attribute, Value>();
-
-    private void checkNulls(Attribute attribute, Value value) {
-        if(attribute == null)
-            throw new NullPointerException("The attribute cannot be null.");
-        if(value == null)
-            throw new NullPointerException(
-                    "The value cannot be null. You may want create a Value object that contains null.");
-    }
-
-    /**
-     * Adds a new <code>attribute</code>-<code>value</code> mapping. The
-     * <code>attribute</code> cannot already exist in the map. To overwrite an existing attribute, use
-     * {@link #addOrChange(Attribute, Value)} instead.
-     *
-     * @param attribute the attribute to add
-     * @param value the value for <code>attribute</code>
-     * @throws IllegalArgumentException if the <code>attribute</code> already exists in this map
-     * @throws NullPointerException if either the <code>attribute</code> or the <code>value</code> is <code>null</code>;
-     * for null value, create a <code>Value</code> object containing <code>null</code>
-     * @see #addOrChange(Attribute, Value)
-     * @see #add(String, Value)
-     * @see #add(Entry)
-     * @see #add(AttributesMap)
-     */
-    public void add(Attribute attribute, Value value) {
-        if(getOrNull(attribute) != null)
-            throw new IllegalArgumentException("Attribute \"" + attribute.getName()
-                    + "\" already exists. Use method addOrChange(Attribute, Value) instead.");
-        checkNulls(attribute, value);
-        map.put(attribute, value);
-    }
-
-    /**
-     * Adds a new attribute mapping to the specified <code>value</code>. Convenient version of
-     * {@link #add(Attribute, Value)}.
-     *
-     * @param name the attribute name
-     * @param value the attribute value
-     * @see #add(Attribute, Value)
-     * @see #addOrChange(String, Value)
-     */
-    public void add(String name, Value value) {
-        add(new Attribute(name), value);
-    }
-
-    /**
-     * Adds a new mapping to this map. Convenient version of {@link #add(Attribute, Value)}.
-     *
-     * @param entry a pair containing both an attribute and a value
-     * @see #add(Attribute, Value)
-     * @see #addOrChange(Entry)
-     */
-    public void add(Entry<Attribute, Value> entry) {
-        add(entry.getKey(), entry.getValue());
-    }
-
-    /**
-     * Adds all entries from another map to this map. This method uses {@link #add(Attribute, Value)}, so it throws an
-     * exception when trying to overwrite an existing attribute.
-     *
-     * @param attributes the map to add
-     * @see #add(Attribute, Value)
-     * @see #addOrChange(AttributesMap)
-     */
-    public void add(AttributesMap attributes) {
-        for(Entry<Attribute, Value> entry : attributes.map.entrySet())
-            add(entry);
-    }
-
-    /**
-     * Adds to this map a new <code>attribute</code> mapping to the specified <code>value</code>. Unlike
-     * {@link #add(Attribute, Value)}, this method overwrites an existing attribute with the same name.
-     *
-     * @param attribute the attribute to add or overwrite
-     * @param value the value for the <code>attribute</code>
-     * @throws NullPointerException if either the <code>attribute</code> or the <code>value</code> is <code>null</code>;
-     * for null value create a <code>Value</code> object containing <code>null</code>
-     * @see #add(Attribute, Value)
-     * @see #addOrChange(String, Value)
-     * @see #addOrChange(Entry)
-     * @see #addOrChange(AttributesMap)
-     */
-    public void addOrChange(Attribute attribute, Value value) {
-        map.put(attribute, value);
-        checkNulls(attribute, value);
-    }
-
-    /**
-     * Adds a new attribute mapping to the specified <code>value</code> or overwrites an existing one. Convenient
-     * version of {@link #addOrChange(Attribute, Value)}.
-     *
-     * @param name the attribute name
-     * @param value the attribute value
-     * @see #addOrChange(Attribute, Value)
-     * @see #add(String, Value)
-     */
-    public void addOrChange(String name, Value value) {
-        addOrChange(new Attribute(name), value);
-    }
-
-    /**
-     * Adds a new mapping to this map or overwrites an existing one with the same attribute name. Convenient version of
-     * {@link #addOrChange(Attribute, Value)}.
-     *
-     * @param entry a pair containing both an attribute and a value
-     * @see #addOrChange(Attribute, Value)
-     * @see #add(Entry)
-     */
-    public void addOrChange(Entry<Attribute, Value> entry) {
-        addOrChange(entry.getKey(), entry.getValue());
-    }
-
-    /**
-     * Adds all entries from another map to this map. If any attribute with the same name exists in this map, it will be
-     * overwritten.
-     *
-     * @param attributes the map to add
-     * @see #addOrChange(Attribute, Value)
-     * @see #add(AttributesMap)
-     */
-    public void addOrChange(AttributesMap attributes) {
-        for(Entry<Attribute, Value> entry : attributes.map.entrySet())
-            addOrChange(entry);
-    }
-
-    private void checkAttribute(Attribute attribute) {
-        if(attribute == null)
-            throw new NullPointerException("The attribute cannot be null.");
-    }
-
-    /**
-     * Gets the value mapped to the specified <code>attribute</code>. If such a mapping does not exist, this method throws
-     * an exception. If this is not an expected behavior, use {@link #getOrNull(Attribute)} instead.
-     *
-     * @param attribute the attribute to obtain
-     * @return the value mapped to <code>attribute</code>
-     * @throws IllegalArgumentException if no value is mapped to <code>attribute</code>
-     * @throws NullPointerException if <code>attribute</code> is <code>null</code>
-     * @see #getOrNull(Attribute)
-     * @see #get(String)
-     */
-    public Value get(Attribute attribute) {
-        Value value = getOrNull(attribute);
-        if(value == null)
-            throw new IllegalArgumentException("Attribute " + attribute.getName()
-                    + " does not exist. Use method getOrNull(Attribute) instead.");
-        return value;
-    }
-
-    /**
-     * Gets the value mapped to the specified attribute. Convenient version of {@link #get(Attribute)}.
-     *
-     * @param name name of the attribute
-     * @return the value mapped to the specified attribute
-     * @see #get(Attribute)
-     * @see #getOrNull(String)
-     */
-    public Value get(String name) {
-        return get(new Attribute(name));
-    }
-
-    /**
-     * Gets the value mapped to the specified <code>attribute</code>. Unlike {@link #get(Attribute)}, this method
-     * returns <code>null</code> if the requested mapping does not exist.
-     *
-     * @param attribute the attribute to obtain
-     * @return the value mapped to <code>attribute</code> or <code>null</code> if it does not exist
-     * @throws NullPointerException if the <code>attribute</code> is <code>null</code>
-     * @see #get(Attribute)
-     * @see #getOrNull(String)
-     */
-    public Value getOrNull(Attribute attribute) {
-        checkAttribute(attribute);
-        return map.get(attribute);
-    }
-
-    /**
-     * Gets the value mapped to the specified attribute. Convenient version of {@link #getOrNull(Attribute)}.
-     *
-     * @param name name of the attribute
-     * @return the value mapped to specified attribute or <code>null</code> if it does not exist
-     * @see #getOrNull(Attribute)
-     * @see #getOr(String)
-     */
-    public Value getOrNull(String name) {
-        return getOrNull(new Attribute(name));
-    }
-
-    /**
-     * Removes the specified <code>attribute</code> and its value from this map. If <code>attribute</code> does not
-     * exist, this method doesn't do anything.
-     *
-     * @param attribute the attribute to remove
-     * @throws NullPointerException if <code>attribute</code> is <code>null</code>
-     * @see #remove(String)
-     */
-    public void remove(Attribute attribute) {
-        checkAttribute(attribute);
-        map.remove(attribute);
-    }
-
-    /**
-     * Removes the specified attribute and its value from this map. Convenient version of {@link #remove(Attribute)}.
-     *
-     * @param name the name of the attribute to remove
-     * @see #remove(Attribute)
-     */
-    public void remove(String name) {
-        map.remove(new Attribute(name));
-    }
-
-    /**
-     * Returns an iterator over all entries stored in this map.
-     *
-     * @return an iterator for this map
-     * @see java.util.Iterator
-     * @see java.lang.Iterable
-     */
-    @Override
-    public Iterator<Entry<Attribute, Value>> iterator() {
-        return map.entrySet().iterator();
-    }
-
-    /**
-     * Creates a copy of this map. Since <code>Value</code> and <code>Attribute</code> are immutable classes, this
-     * method does not clone them.
-     *
-     * @return a copy of this map containing identical entries
-     */
-    @Override
-    public AttributesMap clone() {
-        AttributesMap result = new AttributesMap();
-        result.add(this);
-        return result;
-    }
-
-    /**
-     * Returns a string representation of this map listing all key-value pairs stored in it.
-     *
-     * @return a string representation of this object
-     */
-    @Override
-    public String toString() {
-        return map.toString();
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/IncompatibleTypesException.java b/src/pl/edu/mimuw/cloudatlas/model/IncompatibleTypesException.java
deleted file mode 100644
index 65c719e..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/IncompatibleTypesException.java
+++ /dev/null
@@ -1,81 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import pl.edu.mimuw.cloudatlas.model.Value.Operation;
-
-/**
- * An exception thrown when an unsupported binary operation on values is requested.
- *
- * @see UnsupportedValueOperationException
- * @see UnsupportedConversionException
- */
-@SuppressWarnings("serial")
-public class IncompatibleTypesException extends UnsupportedOperationException {
-    private final Type left;
-    private final Type right;
-    private final Operation operation;
-
-    /**
-     * Creates a new object representing this exception.
-     *
-     * @param left type of a left operand
-     * @param right type of a right operand
-     * @param operation an operation that caused this exception
-     */
-    protected IncompatibleTypesException(Type left, Type right, Operation operation) {
-        super("Incompatible types: " + left + " and " + right + " in operation " + operation + ".");
-        this.left = left;
-        this.right = right;
-        this.operation = operation;
-    }
-
-    /**
-     * Gets the type of the left operand in the operation that caused this exception.
-     *
-     * @return the type of the left operand
-     */
-    public Type getLeft() {
-        return left;
-    }
-
-    /**
-     * Gets the type of the right operand in the operation that caused this exception.
-     *
-     * @return the type of the right operand
-     */
-    public Type getRight() {
-        return right;
-    }
-
-    /**
-     * Gets an object representing the operation that caused this exception.
-     *
-     * @return the operation that caused this exception
-     */
-    public Operation getOperation() {
-        return operation;
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/PathName.java b/src/pl/edu/mimuw/cloudatlas/model/PathName.java
deleted file mode 100644
index 7f3a9ac..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/PathName.java
+++ /dev/null
@@ -1,180 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.List;
-
-/**
- * Represent a fully qualified name of a zone, also known as a global name or a path name. Objects of this class are immutable.
- */
-public class PathName {
-    /**
-     * Object representing the name of the root zone (/).
-     */
-    public static final PathName ROOT = new PathName("/");
-
-    private final List<String> components;
-    private final String name;
-
-    /**
-     * Creates a <code>PathName</code> object representing the specified path. For the root zone, there are three
-     * accepted forms: <code>null</code> reference, empty string or slash. Any other zone is represented by a string
-     * starting with slash and containing names of zones at each level of the hierarchy, separated by slashes. Zone names
-     * must contain only letters and digits.
-     *
-     * @param name path name of a zone, for instance: <code>/warsaw/uw/violet07</code>
-     * @throws IllegalArgumentException if the <code>name</code> is incorrect
-     */
-    public PathName(String name) {
-        // we accept null and "/" as names of a root zone, however, we convert all of them to ""
-        name = name == null || name.equals("/")? "" : name.trim();
-        if(!name.matches("(/\\w+)*"))
-            throw new IllegalArgumentException("Incorrect fully qualified name: " + name + ".");
-        this.name = name;
-        components = name.equals("")? new ArrayList<String>() : Arrays.asList(name.substring(1).split("/"));
-    }
-
-    /**
-     * Creates a <code>PathName</code> object from a collection of zone names. Every zone name must contain only
-     * letters and digits.
-     *
-     * @param components a collection of zone names at subsequent levels of hierarchy (starting from root); an empty
-     * collection represents the root zone
-     * @throws IllegalArgumentException if any zone name is incorrect
-     */
-    public PathName(Collection<String> components) {
-        this.components = new ArrayList<String>(components);
-        if(components.isEmpty())
-            this.name = "";
-        else {
-            String currentName = "";
-            for(String c : components) {
-                currentName += "/" + c;
-                if(!c.matches("\\w+"))
-                    throw new IllegalArgumentException("Incorrect component " + c + ".");
-            }
-            this.name = currentName;
-        }
-    }
-
-    /**
-     * Gets zone names at subsequent levels of hierarchy, starting from the root. For the root zone, this method returns an
-     * empty collection. Modifying the returned list will throw an exception.
-     *
-     * @return a collection of zones names
-     */
-    public List<String> getComponents() {
-        return Collections.unmodifiableList(components);
-    }
-
-    /**
-     * Gets a full path name. For the root zone, this method returns an empty string.
-     *
-     * @return a path name represented by this object
-     * @see #toString()
-     */
-    public String getName() {
-        return name;
-    }
-
-    /**
-     * Gets a name one level up in the hierarchy. For the root zone, this method returns a new instance of the same zone.
-     *
-     * @return a new <code>PathName</code> object representing a zone one level up in the hierarchy
-     */
-    public PathName levelUp() {
-        List<String> componentsUp = new ArrayList<String>(components);
-        if(!componentsUp.isEmpty())
-            componentsUp.remove(componentsUp.size() - 1);
-        return new PathName(componentsUp);
-    }
-
-    /**
-     * Gets a name one level down in a hierarchy.
-     *
-     * @param son zone name at a lower level
-     * @return a new <code>PathName</code> object representing a zone one level down in the hierarchy
-     */
-    public PathName levelDown(String son) {
-        return new PathName(name + "/" + son);
-    }
-
-    /**
-     * Gets a zone name at the lowest level (highest number) in a hierarchy.
-     *
-     * @return a leaf zone
-     * @throws UnsupportedOperationException if this object represents the root zone
-     */
-    public String getSingletonName() {
-        try {
-            return components.get(components.size() - 1);
-        } catch(IndexOutOfBoundsException exception) {
-            throw new UnsupportedOperationException("getSingletonName() is not supported for the root zone.");
-        }
-    }
-
-    /**
-     * Returns a hash code value for this object. This method returns a hash code of a string representing the full path
-     * name.
-     *
-     * @return a hash code for this object
-     */
-    @Override
-    public int hashCode() {
-        return name.hashCode();
-    }
-
-    /**
-     * Indicates whether this object is equal to another. A <code>PathName</code> object is equal to other objects of
-     * the same class representing identical path names.
-     *
-     * @param object the object to check
-     * @return whether <code>object</code>'s name is equal to this one's
-     */
-    @Override
-    public boolean equals(Object object) {
-        if(object == null)
-            return false;
-        if(getClass() != object.getClass())
-            return false;
-        return name.equals(((PathName)object).name);
-    }
-
-    /**
-     * Returns a textual representation for this <code>PathName</code>. For the root zone, unlike {@link #getName()},
-     * this method returns a slash.
-     *
-     * @return a path name for this object
-     * @see #getName()
-     */
-    @Override
-    public String toString() {
-        return name.equals("")? "/" : getName();
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/Type.java b/src/pl/edu/mimuw/cloudatlas/model/Type.java
deleted file mode 100644
index 986db71..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/Type.java
+++ /dev/null
@@ -1,81 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-/**
- * A type of a value that may be stored as an attribute.
- */
-public abstract class Type {
-    /**
-     * A primary type. This is a characteristic that every type has. It can be extended: for instance a collection may
-     * be parameterized with a type of stored values.
-     */
-    public static enum PrimaryType {
-        BOOLEAN, CONTACT, DOUBLE, DURATION, INT, LIST, NULL, SET, STRING, TIME,
-    }
-
-    private final PrimaryType primaryType;
-
-    /**
-     * Creates a <code>Type</code> object with a given primary type.
-     *
-     * @param primaryType a primary type for this type
-     */
-    public Type(PrimaryType primaryType) {
-        this.primaryType = primaryType;
-    }
-
-    /**
-     * Returns the primary type of this type.
-     *
-     * @return a primary type
-     */
-    public PrimaryType getPrimaryType() {
-        return primaryType;
-    }
-
-    /**
-     * Indicates whether this type can be implicitly "cast" to the given one and vice versa. This is introduced to deal with
-     * null values. In practice, two types are compatible either if they are the same or if one them is a special
-     * "null type".
-     *
-     * @param type a type to check
-     * @return whether two types are compatible with each other
-     * @see TypePrimitive#NULL
-     * @see ValueNull
-     */
-    public boolean isCompatible(Type type) {
-        return getPrimaryType() == PrimaryType.NULL || type.getPrimaryType() == PrimaryType.NULL;
-    }
-
-    /**
-     * Indicates whether this type represents a collection.
-     *
-     * @return true for collections, false otherwise
-     */
-    public boolean isCollection() {
-        return false;
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/TypeCollection.java b/src/pl/edu/mimuw/cloudatlas/model/TypeCollection.java
deleted file mode 100644
index da5d848..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/TypeCollection.java
+++ /dev/null
@@ -1,116 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import java.util.Collection;
-
-import pl.edu.mimuw.cloudatlas.model.Type;
-import pl.edu.mimuw.cloudatlas.model.TypePrimitive;
-import pl.edu.mimuw.cloudatlas.model.Value;
-import pl.edu.mimuw.cloudatlas.model.ValueNull;
-
-/**
- * Represents a collection type with a specified element type.
- *
- * @see TypePrimitve
- */
-public class TypeCollection extends Type {
-    private final Type elementType;
-
-    /**
-     * Creates a new collection type.
-     *
-     * @param primaryType a type of this collection (set, list etc.)
-     * @param elementType a type of elements of this collection; may be a complex type (for instance
-     * another <code>TypeCollection</code>)
-     */
-    public TypeCollection(PrimaryType primaryType, Type elementType) {
-        super(primaryType);
-        switch(primaryType) {
-            case LIST:
-            case SET:
-                break;
-            default:
-                throw new IllegalArgumentException("This class can represent a collection only (list, set etc.).");
-        }
-        this.elementType = elementType;
-    }
-
-    /**
-     * Gets a type of elements stored in this collection.
-     *
-     * @return type of element in this collection
-     */
-    public Type getElementType() {
-        return elementType;
-    }
-
-    /**
-     * Returns a textual representation of this collection, for instance: "SET of (STRING)".
-     *
-     * @return a textual representation of this type
-     */
-    @Override
-    public String toString() {
-        return getPrimaryType().toString() + " of (" + elementType.toString() + ")";
-    }
-
-    @Override
-    public boolean isCompatible(Type type) {
-        return super.isCompatible(type)
-                || (getPrimaryType() == type.getPrimaryType() && elementType
-                        .isCompatible(((TypeCollection)type).elementType));
-    }
-
-    @Override
-    public boolean isCollection() {
-        return true;
-    }
-
-    /**
-     * Returns a type of all elements in the specified collection. If the collection is empty, this method returns
-     * {@link TypePrimitive#NULL}. If the collection contains at least two elements of distinct types that are not nulls,
-     * an exception is thrown.
-     *
-     * @param collection a collection of values to check
-     * @return type of elements in this collection
-     * @throws IllegalArgumentException if the collection contains non-null elements of different types
-     */
-    public static Type computeElementType(Collection<Value> collection) {
-        Type mainType = null;
-
-        for(Value v : collection) {
-            if(v.isNull())
-                v = ValueNull.getInstance();
-            if(mainType == null) {
-                if(v.getType().getPrimaryType() != Type.PrimaryType.NULL)
-                    mainType = v.getType();
-            } else if(!mainType.isCompatible(v.getType()))
-                throw new IllegalArgumentException("Collection has non-null elements of different types.");
-        }
-
-        return mainType == null? TypePrimitive.NULL : mainType;
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/TypePrimitive.java b/src/pl/edu/mimuw/cloudatlas/model/TypePrimitive.java
deleted file mode 100644
index ab28cb4..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/TypePrimitive.java
+++ /dev/null
@@ -1,108 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-/**
- * Convenient class for types that just wrap ordinary Java types.
- *
- * @see TypeCollection
- */
-public class TypePrimitive extends Type {
-    /**
-     * Boolean type.
-     */
-    public static final TypePrimitive BOOLEAN = new TypePrimitive(PrimaryType.BOOLEAN);
-
-    /**
-     * Contact type.
-     */
-    public static final TypePrimitive CONTACT = new TypePrimitive(PrimaryType.CONTACT);
-
-    /**
-     * Double type.
-     */
-    public static final TypePrimitive DOUBLE = new TypePrimitive(PrimaryType.DOUBLE);
-
-    /**
-     * Duration type.
-     */
-    public static final TypePrimitive DURATION = new TypePrimitive(PrimaryType.DURATION);
-
-    /**
-     * Integer type.
-     */
-    public static final TypePrimitive INTEGER = new TypePrimitive(PrimaryType.INT);
-
-    /**
-     * A special null type that represents null values of an unknown type. It can be converted to any other type.
-     *
-     * @see Type#isCompatible(Type)
-     * @see ValueNull
-     */
-    public static final TypePrimitive NULL = new TypePrimitive(PrimaryType.NULL);
-
-    /**
-     * String type.
-     */
-    public static final TypePrimitive STRING = new TypePrimitive(PrimaryType.STRING);
-
-    /**
-     * Time type.
-     */
-    public static final TypePrimitive TIME = new TypePrimitive(PrimaryType.TIME);
-
-    private TypePrimitive(PrimaryType primaryType) {
-        super(primaryType);
-        switch(primaryType) {
-            case BOOLEAN:
-            case CONTACT:
-            case DOUBLE:
-            case DURATION:
-            case INT:
-            case NULL:
-            case STRING:
-            case TIME:
-                break;
-            default:
-                throw new IllegalArgumentException(
-                        "This class can represent a primitive type only (boolean, int etc.).");
-        }
-    }
-
-    /**
-     * Gets a textual representation of this type.
-     *
-     * @return a string representing this type
-     */
-    @Override
-    public String toString() {
-        return getPrimaryType().toString();
-    }
-
-    @Override
-    public boolean isCompatible(Type type) {
-        return super.isCompatible(type) || getPrimaryType() == type.getPrimaryType();
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/UnsupportedConversionException.java b/src/pl/edu/mimuw/cloudatlas/model/UnsupportedConversionException.java
deleted file mode 100644
index 6f30360..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/UnsupportedConversionException.java
+++ /dev/null
@@ -1,67 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-/**
- * An exception describing an unsupported conversion of a value to another type.
- *
- * @see IncompatibleTypesException
- * @see UnsupportedValueOperationException
- */
-@SuppressWarnings("serial")
-public class UnsupportedConversionException extends UnsupportedOperationException {
-    private final Type from;
-    private final Type to;
-
-    /**
-     * Creates a new instance of this this exception.
-     *
-     * @param from source type of an unsupported conversion
-     * @param to destination type of an unsupported conversion
-     */
-    protected UnsupportedConversionException(Type from, Type to) {
-        super("Type " + from + " cannot be converted to " + to + ".");
-        this.from = from;
-        this.to = to;
-    }
-
-    /**
-     * Gets the source type of the unsupported conversion that caused this exception.
-     *
-     * @return source type
-     */
-    public Type getFrom() {
-        return from;
-    }
-
-    /**
-     * Gets the destination type of the unsupported conversion that caused this exception.
-     *
-     * @return destination type
-     */
-    public Type getTo() {
-        return to;
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/UnsupportedValueOperationException.java b/src/pl/edu/mimuw/cloudatlas/model/UnsupportedValueOperationException.java
deleted file mode 100644
index bb3aa1f..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/UnsupportedValueOperationException.java
+++ /dev/null
@@ -1,69 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import pl.edu.mimuw.cloudatlas.model.Value.Operation;
-
-/**
- * An exception caused by calling an unsupported unary operation on value.
- *
- * @see IncompatibleTypesException
- * @see UnsupportedConversionException
- */
-@SuppressWarnings("serial")
-public class UnsupportedValueOperationException extends UnsupportedOperationException {
-    private final Type left;
-    private final Operation operation;
-
-    /**
-     * Creates a new object representing this exception.
-     *
-     * @param left type of a value that was an argument of an operation that caused this exception
-     * @param operation the operation that caused this exception
-     */
-    protected UnsupportedValueOperationException(Type left, Operation operation) {
-        super("Type: " + left + " does not provide operation " + operation + ".");
-        this.left = left;
-        this.operation = operation;
-    }
-
-    /**
-     * Gets the type of value that was the argument to the operation that caused this exception.
-     *
-     * @return first argument of the operation
-     */
-    public Type getLeft() {
-        return left;
-    }
-
-    /**
-     * Gets the operation that caused this exception.
-     *
-     * @return the operation
-     */
-    public Operation getOperation() {
-        return operation;
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/Value.java b/src/pl/edu/mimuw/cloudatlas/model/Value.java
deleted file mode 100644
index c4054cf..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/Value.java
+++ /dev/null
@@ -1,241 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import pl.edu.mimuw.cloudatlas.model.Value;
-
-/**
- * A single value stored as an attribute.
- */
-public abstract class Value {
-    /**
-     * An operation that may be performed on values.
-     */
-    public enum Operation {
-        EQUAL, COMPARE, ADD, SUBTRACT, MULTIPLY, DIVIDE, MODULO, AND, OR, REG_EXPR, NEGATE, VALUE_SIZE,
-    }
-
-    /**
-     * Gets the type of this value.
-     *
-     * @return type of this value
-     */
-    public abstract Type getType();
-
-    /**
-     * Indicates whether this value is null. Distinct from a <code>Value</code> reference that is <code>null</code>
-     * itself.
-     *
-     * @return true if and only if this value is null
-     */
-    public abstract boolean isNull();
-
-    protected final void sameTypesOrThrow(Value value, Operation operation) {
-        if(!getType().isCompatible(value.getType()))
-            throw new IncompatibleTypesException(getType(), value.getType(), operation);
-    }
-
-    /**
-     * Checks whether this value is equal to the specified one (operator ==).
-     *
-     * @param value the right side of the operator
-     * @return a <code>ValueBoolean</code> representing true if and only if both values are equal
-     * @throws UnsupportedValueOperationException if this operation is unsupported for these values
-     */
-    public Value isEqual(Value value) {
-        throw new UnsupportedValueOperationException(getType(), Operation.EQUAL);
-    }
-
-    /**
-     * Indicates whether this object is equal to another one.
-     *
-     * @param object the object to check
-     * @return whether two objects are equal
-     */
-    @Override
-    public boolean equals(Object object) {
-        if(!(object instanceof Value))
-            return false;
-        return ((ValueBoolean)isEqual((Value)object)).getValue();
-    }
-
-    /**
-     * Checks whether this value is lower than the specified one (operator <=).
-     *
-     * @param value the right side of the operator
-     * @return a <code>ValueBoolean</code> representing true if and only if this value is lower than the provided one
-     * @throws UnsupportedValueOperationException if this operator is unsupported for these values (for example
-     * incompatible or non-numeric types)
-     */
-    public Value isLowerThan(Value value) {
-        throw new UnsupportedValueOperationException(getType(), Operation.COMPARE);
-    }
-
-    /**
-     * Returns a new value created by adding argument to this value (operator +).
-     *
-     * @param value the right side of the operator
-     * @return a sum of two values
-     * @throws UnsupportedValueOperationException if this operator is unsupported for these values (for example
-     * incompatible or non-numeric types)
-     */
-    public Value addValue(Value value) {
-        // name clash with add from List interface
-        throw new UnsupportedValueOperationException(getType(), Operation.ADD);
-    }
-
-    /**
-     * Returns a new value created by subtracting argument from this value (operator -).
-     *
-     * @param value the right side of the operator
-     * @return a difference of two values
-     * @throws UnsupportedValueOperationException if this operator is unsupported for these values (for example
-     * incompatible or non-numeric types)
-     */
-    public Value subtract(Value value) {
-        throw new UnsupportedValueOperationException(getType(), Operation.SUBTRACT);
-    }
-
-    /**
-     * Returns a new value created by multiplying this value by an argument (operator *).
-     *
-     * @param value the right side of the operator
-     * @return a product of two values
-     * @throws UnsupportedValueOperationException if this operator is unsupported for these values (for example
-     * incompatible or non-numeric types)
-     */
-    public Value multiply(Value value) {
-        throw new UnsupportedValueOperationException(getType(), Operation.MULTIPLY);
-    }
-
-    /**
-     * Returns a new value created by dividing this value by an argument (operator /).
-     *
-     * @param value the right side of the operator
-     * @return a quotient of two values
-     * @throws UnsupportedValueOperationException if this operator is unsupported for these values (for example
-     * incompatible or non-numeric types)
-     */
-    public Value divide(Value value) {
-        throw new UnsupportedValueOperationException(getType(), Operation.DIVIDE);
-    }
-
-    /**
-     * Returns the remainder of division of this value by an argument (operator %).
-     *
-     * @param value the right side of the operator
-     * @return a remainder
-     * @throws UnsupportedValueOperationException if this operator is unsupported for these values (for example
-     * incompatible or non-numeric types)
-     */
-    public Value modulo(Value value) {
-        throw new UnsupportedValueOperationException(getType(), Operation.MODULO);
-    }
-
-    /**
-     * Returns the result of a logical AND (operator &&).
-     *
-     * @param value the right side of the operator
-     * @return a conjunction of the two values
-     * @throws UnsupportedValueOperationException if this operator is unsupported for these values (for example
-     * non-boolean types)
-     */
-    public Value and(Value value) {
-        throw new UnsupportedValueOperationException(getType(), Operation.AND);
-    }
-
-    /**
-     * Returns the result of a logical OR (operator ||).
-     *
-     * @param value the right side of the operator
-     * @return an alternative of two values
-     * @throws UnsupportedValueOperationException if this operator is unsupported for these values (for example
-     * non-boolean types)
-     */
-    public Value or(Value value) {
-        throw new UnsupportedValueOperationException(getType(), Operation.OR);
-    }
-
-    /**
-     * Returns a result of trying to match to this value with a regular expression specified as an argument.
-     *
-     * @param value the regular expression to match against
-     * @return a <code>ValueBoolean</code> representing true if and only if this value matches provided regular
-     * expression
-     * @throws UnsupportedValueOperationException if this operator is unsupported for these values
-     */
-    public Value regExpr(Value value) {
-        throw new UnsupportedValueOperationException(getType(), Operation.REG_EXPR);
-    }
-
-    /**
-     * Returns the negation (numeric or logical) of this value. This may refer to operator - or !, depending on type.
-     *
-     * @return a value that is the negation of this value
-     * @throws UnsupportedValueOperationException if this operator is unsupported for this value
-     */
-    public Value negate() { // !, -
-        throw new UnsupportedValueOperationException(getType(), Operation.NEGATE);
-    }
-
-    /**
-     * Returns the size of this value. Semantics depend on type.
-     *
-     * @return a size of this value
-     * @throws UnsupportedValueOperationException if this operation is unsupported for this value
-     */
-    public Value valueSize() {
-        // name clash with size from List interface
-        throw new UnsupportedValueOperationException(getType(), Operation.VALUE_SIZE);
-    }
-
-    /**
-     * Returns this value converted to another type.
-     *
-     * @param to a desired type
-     * @return this value converted to the <code>type</code>
-     * @throws UnsupportedConversionException if a requested conversion is unsupported
-     */
-    public abstract Value convertTo(Type to);
-
-    /**
-     * Returns a textual representation of this value. This method uses conversion to <code>ValueString</code>.
-     *
-     * @return a textual representation of this value
-     * @see #convertTo(Type)
-     */
-    @Override
-    public String toString() {
-        return ((ValueString)convertTo(TypePrimitive.STRING)).getValue();
-    }
-
-    /**
-     * Returns a default value (such as an uninitialized variable). This may be <code>0</code> for integer types,
-     * <code>false</code> for boolean, <code>null</code> for complex types, etc.
-     *
-     * @return a default value of this type
-     */
-    public abstract Value getDefaultValue();
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/ValueBoolean.java b/src/pl/edu/mimuw/cloudatlas/model/ValueBoolean.java
deleted file mode 100644
index 57078c2..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/ValueBoolean.java
+++ /dev/null
@@ -1,93 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import pl.edu.mimuw.cloudatlas.model.Value;
-import pl.edu.mimuw.cloudatlas.model.ValueBoolean;
-
-/**
- * A class that wraps a Java <code>Boolean</code> object.
- */
-public class ValueBoolean extends ValueSimple<Boolean> {
-    /**
-     * Constructs a new <code>ValueBoolean</code> object wrapping the specified <code>value</code>.
-     *
-     * @param value the value to wrap
-     */
-    public ValueBoolean(Boolean value) {
-        super(value);
-    }
-
-    @Override
-    public Type getType() {
-        return TypePrimitive.BOOLEAN;
-    }
-
-    @Override
-    public Value getDefaultValue() {
-        return new ValueBoolean(false);
-    }
-
-    @Override
-    public ValueBoolean isLowerThan(Value value) {
-        sameTypesOrThrow(value, Operation.COMPARE);
-        if(isNull() || value.isNull())
-            return new ValueBoolean(null);
-        return new ValueBoolean(!getValue() && ((ValueBoolean)value).getValue());
-    }
-
-    @Override
-    public ValueBoolean and(Value value) {
-        sameTypesOrThrow(value, Operation.AND);
-        if(isNull() || value.isNull())
-            return new ValueBoolean(null);
-        return new ValueBoolean(getValue() && ((ValueBoolean)value).getValue());
-    }
-
-    @Override
-    public ValueBoolean or(Value value) {
-        sameTypesOrThrow(value, Operation.OR);
-        if(isNull() || value.isNull())
-            return new ValueBoolean(null);
-        return new ValueBoolean(getValue() || ((ValueBoolean)value).getValue());
-    }
-
-    @Override
-    public ValueBoolean negate() {
-        return new ValueBoolean(isNull()? null : !getValue());
-    }
-
-    @Override
-    public Value convertTo(Type type) {
-        switch(type.getPrimaryType()) {
-            case BOOLEAN:
-                return this;
-            case STRING:
-                return getValue() == null? ValueString.NULL_STRING : new ValueString(getValue().toString());
-            default:
-                throw new UnsupportedConversionException(getType(), type);
-        }
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/ValueContact.java b/src/pl/edu/mimuw/cloudatlas/model/ValueContact.java
deleted file mode 100644
index 670a025..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/ValueContact.java
+++ /dev/null
@@ -1,100 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import java.net.InetAddress;
-
-import pl.edu.mimuw.cloudatlas.model.Value;
-import pl.edu.mimuw.cloudatlas.model.ValueContact;
-
-/**
- * A class that represents a contact to a node. The contact consists of a full path name of this node and its IP
- * address.
- * <p>
- * This class is immutable.
- */
-public class ValueContact extends Value {
-    private final PathName name;
-    private final InetAddress address;
-
-    /**
-     * Constructs a new <code>ValueContact</code> with the specified path name and IP address.
-     *
-     * @param name the full path name of a node
-     * @param address the IP address of the node
-     */
-    public ValueContact(PathName name, InetAddress address) {
-        this.name = name;
-        this.address = address;
-    }
-
-    @Override
-    public Value getDefaultValue() {
-        return new ValueContact(null, null);
-    }
-
-    /**
-     * Returns a name stored in this object.
-     *
-     * @return the name of a node
-     */
-    public PathName getName() {
-        return name;
-    }
-
-    /**
-     * Returns an IP address stored in this object.
-     *
-     * @return the IP address of a node
-     */
-    public InetAddress getAddress() {
-        return address;
-    }
-
-    @Override
-    public Type getType() {
-        return TypePrimitive.CONTACT;
-    }
-
-    @Override
-    public Value convertTo(Type type) {
-        switch(type.getPrimaryType()) {
-            case CONTACT:
-                return this;
-            case STRING:
-                if(isNull())
-                    return ValueString.NULL_STRING;
-                else
-                    return new ValueString("(" + name.toString() + ", " + address.toString() + ")");
-            default:
-                throw new UnsupportedConversionException(getType(), type);
-        }
-    }
-
-    @Override
-    public boolean isNull() {
-        return name == null || address == null;
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/ValueDouble.java b/src/pl/edu/mimuw/cloudatlas/model/ValueDouble.java
deleted file mode 100644
index 920a8ef..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/ValueDouble.java
+++ /dev/null
@@ -1,111 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import pl.edu.mimuw.cloudatlas.model.Value;
-import pl.edu.mimuw.cloudatlas.model.ValueDouble;
-
-/**
- * A class that wraps a Java <code>Double</code> object.
- */
-public class ValueDouble extends ValueSimple<Double> {
-    /**
-     * Constructs a new <code>ValueDouble</code> object wrapping the specified <code>value</code>.
-     *
-     * @param value the value to wrap
-     */
-    public ValueDouble(Double value) {
-        super(value);
-    }
-
-    @Override
-    public Type getType() {
-        return TypePrimitive.DOUBLE;
-    }
-
-    @Override
-    public Value getDefaultValue() {
-        return new ValueDouble(0.0);
-    }
-
-    @Override
-    public ValueBoolean isLowerThan(Value value) {
-        sameTypesOrThrow(value, Operation.COMPARE);
-        if(isNull() || value.isNull())
-            return new ValueBoolean(null);
-        return new ValueBoolean(getValue() < ((ValueDouble)value).getValue());
-    }
-
-    @Override
-    public ValueDouble addValue(Value value) {
-        sameTypesOrThrow(value, Operation.ADD);
-        if(isNull() || value.isNull())
-            return new ValueDouble(null);
-        return new ValueDouble(getValue() + ((ValueDouble)value).getValue());
-    }
-
-    @Override
-    public ValueDouble subtract(Value value) {
-        sameTypesOrThrow(value, Operation.SUBTRACT);
-        if(isNull() || value.isNull())
-            return new ValueDouble(null);
-        return new ValueDouble(getValue() - ((ValueDouble)value).getValue());
-    }
-
-    @Override
-    public ValueDouble multiply(Value value) {
-        sameTypesOrThrow(value, Operation.MULTIPLY);
-        if(isNull() || value.isNull())
-            return new ValueDouble(null);
-        return new ValueDouble(getValue() * ((ValueDouble)value).getValue());
-    }
-
-    @Override
-    public ValueDouble divide(Value value) {
-        sameTypesOrThrow(value, Operation.DIVIDE);
-        if(isNull() || value.isNull())
-            return new ValueDouble(null);
-        return new ValueDouble(getValue() / ((ValueDouble)value).getValue());
-    }
-
-    @Override
-    public ValueDouble negate() {
-        return new ValueDouble(isNull()? null : -getValue());
-    }
-
-    @Override
-    public Value convertTo(Type type) {
-        switch(type.getPrimaryType()) {
-            case DOUBLE:
-                return this;
-            case INT:
-                return new ValueInt(getValue() == null? null : getValue().longValue());
-            case STRING:
-                return getValue() == null? ValueString.NULL_STRING : new ValueString(getValue().toString());
-            default:
-                throw new UnsupportedConversionException(getType(), type);
-        }
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/ValueDuration.java b/src/pl/edu/mimuw/cloudatlas/model/ValueDuration.java
deleted file mode 100644
index bf9d0e0..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/ValueDuration.java
+++ /dev/null
@@ -1,272 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import java.lang.IllegalArgumentException;
-import java.text.ParseException;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
-
-/**
- * A class representing duration in milliseconds. The duration can be negative. This is a simple wrapper of a Java
- * <code>Long</code> object.
- */
-public class ValueDuration extends ValueSimple<Long> {
-    public static class InvalidFormatException extends IllegalArgumentException {
-    }
-
-    /**
-     * Regex pattern for duration strings.
-     */
-    private static final Pattern DURATION_PATTERN = Pattern.compile(
-        "(?<sign>[+-])(?<days>\\d+) " +
-        "(?<hours>[0-1][0-9]|2[0-3]):(?<minutes>[0-5][0-9]):(?<seconds>[0-5][0-9])." +
-        "(?<milliseconds>[0-9]{3})"
-    );
-
-    /**
-     * Constructs a new <code>ValueDuration</code> object wrapping the specified <code>value</code>.
-     *
-     * @param value the value to wrap
-     */
-    public ValueDuration(Long value) {
-        super(value);
-    }
-
-    @Override
-    public Type getType() {
-        return TypePrimitive.DURATION;
-    }
-
-    @Override
-    public Value getDefaultValue() {
-        return new ValueDuration(0l);
-    }
-
-    /**
-     * Constructs a new <code>ValueDuration</code> object from the specified amounts of different time units.
-     *
-     * @param seconds a number of full seconds
-     * @param milliseconds a number of milliseconds (an absolute value does not have to be lower than 1000)
-     */
-    public ValueDuration(long seconds, long milliseconds) {
-        this(seconds * 1000l + milliseconds);
-    }
-
-    /**
-     * Constructs a new <code>ValueDuration</code> object from the specified amounts of different time units.
-     *
-     * @param minutes a number of full minutes
-     * @param seconds a number of full seconds (an absolute value does not have to be lower than 60)
-     * @param milliseconds a number of milliseconds (an absolute value does not have to be lower than 1000)
-     */
-    public ValueDuration(long minutes, long seconds, long milliseconds) {
-        this(minutes * 60l + seconds, milliseconds);
-    }
-
-    /**
-     * Constructs a new <code>ValueDuration</code> object from the specified amounts of different time units.
-     *
-     * @param hours a number of full hours
-     * @param minutes a number of full minutes (an absolute value does not have to be lower than 60)
-     * @param seconds a number of full seconds (an absolute value does not have to be lower than 60)
-     * @param milliseconds a number of milliseconds (an absolute value does not have to be lower than 1000)
-     */
-    public ValueDuration(long hours, long minutes, long seconds, long milliseconds) {
-        this(hours * 60l + minutes, seconds, milliseconds);
-    }
-
-    /**
-     * Constructs a new <code>ValueDuration</code> object from the specified amounts of different time units.
-     *
-     * @param days a number of full days
-     * @param hours a number of full hours (an absolute value does not have to be lower than 24)
-     * @param minutes a number of full minutes (an absolute value does not have to be lower than 60)
-     * @param seconds a number of full seconds (an absolute value does not have to be lower than 60)
-     * @param milliseconds a number of milliseconds (an absolute value does not have to be lower than 1000)
-     */
-    public ValueDuration(long days, long hours, long minutes, long seconds, long milliseconds) {
-        this(days * 24l + hours, minutes, seconds, milliseconds);
-    }
-
-    /**
-     * Constructs a new <code>ValueDuration</code> object from its textual representation. The representation has
-     * format: <code>sd hh:mm:ss.lll</code> where:
-     * <ul>
-     * <li><code>s</code> is a sign (<code>+</code> or <code>-</code>),</li>
-     * <li><code>d</code> is a number of days,</li>
-     * <li><code>hh</code> is a number of hours (between <code>00</code> and <code>23</code>),</li>
-     * <li><code>mm</code> is a number of minutes (between <code>00</code> and <code>59</code>),</li>
-     * <li><code>ss</code> is a number of seconds (between <code>00</code> and <code>59</code>),</li>
-     * <li><code>lll</code> is a number of milliseconds (between <code>000</code> and <code>999</code>).</li>
-     * </ul>
-     * <p>
-     * All fields are obligatory.
-     *
-     * @param value a textual representation of a duration
-     * @throws IllegalArgumentException if <code>value</code> does not meet described rules
-     */
-    public ValueDuration(String value) {
-        this(parseDuration(value));
-    }
-
-    private static long parseDuration(String value) {
-        Matcher matcher = DURATION_PATTERN.matcher(value);
-        if (!matcher.matches()) {
-            throw new InvalidFormatException();
-        }
-
-        long result = parseLongGroup(matcher, "days");
-        result *= 24;
-        result += parseLongGroup(matcher, "hours");
-        result *= 60;
-        result += parseLongGroup(matcher, "minutes");
-        result *= 60;
-        result += parseLongGroup(matcher, "seconds");
-        result *= 1000;
-        result += parseLongGroup(matcher, "milliseconds");
-        result *= matcher.group("sign").equals("+") ? 1 : -1;
-
-        return result;
-    }
-
-    private static long parseLongGroup(Matcher matcher, String group) {
-        return Long.parseLong(matcher.group(group));
-    }
-
-    @Override
-    public ValueBoolean isLowerThan(Value value) {
-        sameTypesOrThrow(value, Operation.COMPARE);
-        if(isNull() || value.isNull())
-            return new ValueBoolean(null);
-        return new ValueBoolean(getValue() < ((ValueDuration)value).getValue());
-    }
-
-    @Override
-    public ValueDuration addValue(Value value) {
-        sameTypesOrThrow(value, Operation.ADD);
-        if (isNull() || value.isNull()) {
-            return new ValueDuration((Long) null);
-        }
-
-        return new ValueDuration(getValue() + ((ValueDuration)value).getValue());
-    }
-
-    @Override
-    public ValueDuration subtract(Value value) {
-        sameTypesOrThrow(value, Operation.SUBTRACT);
-        if (isNull() || value.isNull())
-            return new ValueDuration((Long) null);
-        return new ValueDuration(getValue() - ((ValueDuration)value).getValue());
-    }
-
-    @Override
-    public ValueDuration multiply(Value value) {
-        if (!value.getType().isCompatible(TypePrimitive.INTEGER)) {
-            throw new IncompatibleTypesException(getType(), value.getType(), Operation.MULTIPLY);
-        }
-
-        if (isNull() || value.isNull()) {
-            return new ValueDuration((Long) null);
-        }
-
-        return new ValueDuration(getValue() * ((ValueInt)value).getValue());
-    }
-
-    @Override
-    public Value divide(Value value) {
-        if (!value.getType().isCompatible(TypePrimitive.INTEGER)) {
-            throw new IncompatibleTypesException(getType(), value.getType(), Operation.MULTIPLY);
-        }
-
-        if (isNull() || value.isNull()) {
-            return new ValueDuration((Long) null);
-        }
-
-        if (((ValueInt)value).getValue() == 0l) {
-            throw new ArithmeticException("Division by zero.");
-        }
-
-        return new ValueDuration(getValue() / ((ValueInt)value).getValue());
-    }
-
-    @Override
-    public ValueDuration modulo(Value value) {
-        if (!value.getType().isCompatible(TypePrimitive.INTEGER)) {
-            throw new IncompatibleTypesException(getType(), value.getType(), Operation.MULTIPLY);
-        }
-
-        if (isNull() || value.isNull()) {
-            return new ValueDuration((Long) null);
-        }
-
-        if (((ValueInt)value).getValue() == 0l) {
-            throw new ArithmeticException("Division by zero.");
-        }
-
-        return new ValueDuration(getValue() % ((ValueInt)value).getValue());
-    }
-
-    @Override
-    public ValueDuration negate() {
-        if(isNull()) {
-            return new ValueDuration((Long) null);
-        }
-
-        return new ValueDuration(-getValue());
-    }
-
-    public String toString() {
-        long remainingUnits = getValue();
-        boolean positive = remainingUnits >= 0;
-        remainingUnits = positive ? remainingUnits : -remainingUnits;
-
-        long milliseconds = remainingUnits % 1000;
-        remainingUnits /= 1000;
-        long seconds = remainingUnits % 60;
-        remainingUnits /= 60;
-        long minutes = remainingUnits % 60;
-        remainingUnits /= 60;
-        long hours = remainingUnits % 24;
-        remainingUnits /= 24;
-        long days = remainingUnits;
-
-        return (positive ? "+" : "-") + Long.toString(days) + " " + Long.toString(hours)
-            + ":" + Long.toString(minutes) + ":" + Long.toString(seconds) + "." +
-            Long.toString(milliseconds);
-    }
-
-    @Override
-    public Value convertTo(Type type) {
-        switch(type.getPrimaryType()) {
-            case STRING:
-                return getValue() == null? ValueString.NULL_STRING : new ValueString(toString());
-            case DURATION:
-                return this;
-            default:
-                throw new UnsupportedConversionException(getType(), type);
-        }
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/ValueInt.java b/src/pl/edu/mimuw/cloudatlas/model/ValueInt.java
deleted file mode 100644
index 8811d57..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/ValueInt.java
+++ /dev/null
@@ -1,133 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import pl.edu.mimuw.cloudatlas.model.Type.PrimaryType;
-import pl.edu.mimuw.cloudatlas.model.Value;
-import pl.edu.mimuw.cloudatlas.model.ValueInt;
-
-/**
- * A class that wraps a Java <code>Long</code> object.
- */
-public class ValueInt extends ValueSimple<Long> {
-    /**
-     * Constructs a new <code>ValueInt</code> object wrapping the specified <code>value</code>.
-     *
-     * @param value the value to wrap
-     */
-    public ValueInt(Long value) {
-        super(value);
-    }
-
-    @Override
-    public Type getType() {
-        return TypePrimitive.INTEGER;
-    }
-
-    @Override
-    public Value getDefaultValue() {
-        return new ValueInt(0l);
-    }
-
-    @Override
-    public ValueBoolean isLowerThan(Value value) {
-        sameTypesOrThrow(value, Operation.COMPARE);
-        if(isNull() || value.isNull())
-            return new ValueBoolean(null);
-        return new ValueBoolean(getValue() < ((ValueInt)value).getValue());
-    }
-
-    @Override
-    public ValueInt addValue(Value value) {
-        sameTypesOrThrow(value, Operation.ADD);
-        if(isNull() || value.isNull())
-            return new ValueInt(null);
-        return new ValueInt(getValue() + ((ValueInt)value).getValue());
-    }
-
-    @Override
-    public ValueInt subtract(Value value) {
-        sameTypesOrThrow(value, Operation.SUBTRACT);
-        if(isNull() || value.isNull())
-            return new ValueInt(null);
-        return new ValueInt(getValue() - ((ValueInt)value).getValue());
-    }
-
-    @Override
-    public Value multiply(Value value) {
-        if(value.getType().getPrimaryType() == PrimaryType.DURATION)
-            return value.multiply(this);
-        sameTypesOrThrow(value, Operation.MULTIPLY);
-        if(isNull() || value.isNull())
-            return new ValueInt(null);
-        return new ValueInt(getValue() * ((ValueInt)value).getValue());
-    }
-
-    @Override
-    public ValueDouble divide(Value value) {
-        sameTypesOrThrow(value, Operation.DIVIDE);
-        if(value.isNull())
-            return new ValueDouble(null);
-        if(((ValueInt)value).getValue() == 0l)
-            throw new ArithmeticException("Division by zero.");
-        if(isNull())
-            return new ValueDouble(null);
-        return new ValueDouble((double)getValue() / ((ValueInt)value).getValue());
-    }
-
-    @Override
-    public ValueInt modulo(Value value) {
-        sameTypesOrThrow(value, Operation.MODULO);
-        if(value.isNull())
-            return new ValueInt(null);
-        if(((ValueInt)value).getValue() == 0l)
-            throw new ArithmeticException("Division by zero.");
-        if(isNull())
-            return new ValueInt(null);
-        return new ValueInt(getValue() % ((ValueInt)value).getValue());
-    }
-
-    @Override
-    public ValueInt negate() {
-        return new ValueInt(isNull()? null : -getValue());
-    }
-
-    @Override
-    public Value convertTo(Type type) {
-        switch(type.getPrimaryType()) {
-            case DOUBLE:
-                return new ValueDouble(getValue() == null? null : getValue().doubleValue());
-            case DURATION:
-                return new ValueDuration(getValue());
-            case INT:
-                return this;
-            case STRING:
-                return getValue() == null? ValueString.NULL_STRING : new ValueString(Long.toString(getValue()
-                        .longValue()));
-            default:
-                throw new UnsupportedConversionException(getType(), type);
-        }
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/ValueList.java b/src/pl/edu/mimuw/cloudatlas/model/ValueList.java
deleted file mode 100644
index 76d59ff..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/ValueList.java
+++ /dev/null
@@ -1,275 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.HashSet;
-import java.util.Iterator;
-import java.util.List;
-import java.util.ListIterator;
-import java.util.Set;
-
-import pl.edu.mimuw.cloudatlas.model.TypeCollection;
-import pl.edu.mimuw.cloudatlas.model.Value;
-import pl.edu.mimuw.cloudatlas.model.ValueList;
-
-/**
- * A value representing a list of values of the specified type. Implements <code>List</code> interface.
- * <p>
- * All constructors take a type of elements stored in this list. This type is checked when adding elements to the list
- * and an <code>IllegalArgumentException</code> is thrown in case of a mismatch.
- *
- * @see java.util.List
- */
-public class ValueList extends ValueSimple<List<Value>> implements List<Value> {
-    private TypeCollection type;
-
-    /**
-     * Creates a new <code>ValueList</code> containing all the elements in the specified list.
-     *
-     * @param value a list which content will be copied to this value
-     * @param elementType type of elements stored in this list
-     */
-    public ValueList(List<Value> value, Type elementType) {
-        this(elementType);
-        if(value != null)
-            setValue(value);
-    }
-
-    /**
-     * Creates an empty list.
-     *
-     * @param elementType type of elements stored in this list
-     */
-    public ValueList(Type elementType) {
-        super(new ArrayList<Value>());
-        type = new TypeCollection(Type.PrimaryType.LIST, elementType);
-    }
-
-    @Override
-    public Type getType() {
-        return type;
-    }
-
-    @Override
-    public Value getDefaultValue() {
-        return new ValueList(((TypeCollection)this.getType()).getElementType());
-    }
-
-    /**
-     * Gets a <code>List</code> containing all the objects stored in this value. Modifying the returned list will cause an
-     * exception.
-     */
-    @Override
-    public List<Value> getValue() {
-        return getList() == null? null : Collections.unmodifiableList(getList());
-    }
-
-    @Override
-    public ValueList addValue(Value value) {
-        sameTypesOrThrow(value, Operation.ADD);
-        if(isNull() || value.isNull())
-            return new ValueList(null, ((TypeCollection)getType()).getElementType());
-        List<Value> result = new ArrayList<Value>(getValue());
-        result.addAll(((ValueList)value).getValue());
-        return new ValueList(result, ((TypeCollection)getType()).getElementType());
-    }
-
-    @Override
-    public Value convertTo(Type type) {
-        switch(type.getPrimaryType()) {
-            case LIST:
-                if(getType().isCompatible(type))
-                    return this;
-                throw new UnsupportedConversionException(getType(), type);
-            case SET:
-                if(this.type.getElementType().isCompatible(((TypeCollection)type).getElementType())) {
-                    if(this.isNull())
-                        return new ValueSet(null, this.type.getElementType());
-                    Set<Value> set = new HashSet<Value>();
-                    set.addAll(this);
-                    return new ValueSet(set, this.type.getElementType());
-                }
-                throw new UnsupportedConversionException(getType(), type);
-            case STRING:
-                return getValue() == null? ValueString.NULL_STRING : new ValueString(getValue().toString());
-            default:
-                throw new UnsupportedConversionException(getType(), type);
-        }
-    }
-
-    @Override
-    public ValueInt valueSize() {
-        return new ValueInt((getList() == null? null : (long)getList().size()));
-    }
-
-    @Override
-    public void setValue(List<Value> list) {
-        if(list == null)
-            super.setValue(null);
-        else {
-            super.setValue(new ArrayList<Value>());
-            for(Value e : list)
-                add(e);
-        }
-    }
-
-    private List<Value> getList() {
-        return super.getValue();
-    }
-
-    private void checkElement(Value element) {
-        if(element == null)
-            throw new IllegalArgumentException("If you want to use null, create an object containing null instead.");
-        if(!type.getElementType().isCompatible(element.getType()))
-            throw new IllegalArgumentException("This list contains elements of type "
-                    + type.getElementType().toString() + " only. Incompatible with elements of type: "
-                    + element.getType().toString());
-    }
-
-    @Override
-    public boolean add(Value e) {
-        checkElement(e);
-        return getList().add(e);
-    }
-
-    @Override
-    public void add(int index, Value element) {
-        checkElement(element);
-        getList().add(index, element);
-    }
-
-    @Override
-    public boolean addAll(Collection<? extends Value> c) {
-        for(Value e : c)
-            checkElement(e);
-        return getList().addAll(c);
-    }
-
-    @Override
-    public boolean addAll(int index, Collection<? extends Value> c) {
-        for(Value e : c)
-            checkElement(e);
-        return getList().addAll(index, c);
-    }
-
-    @Override
-    public void clear() {
-        getList().clear();
-    }
-
-    @Override
-    public boolean contains(Object o) {
-        return getList().contains(o);
-    }
-
-    @Override
-    public boolean containsAll(Collection<?> c) {
-        return getList().containsAll(c);
-    }
-
-    @Override
-    public Value get(int index) {
-        return getList().get(index);
-    }
-
-    @Override
-    public int indexOf(Object o) {
-        return getList().indexOf(o);
-    }
-
-    @Override
-    public boolean isEmpty() {
-        return getList().isEmpty();
-    }
-
-    @Override
-    public Iterator<Value> iterator() {
-        return getList().iterator();
-    }
-
-    @Override
-    public int lastIndexOf(Object o) {
-        return getList().lastIndexOf(o);
-    }
-
-    @Override
-    public ListIterator<Value> listIterator() {
-        return getList().listIterator();
-    }
-
-    @Override
-    public ListIterator<Value> listIterator(int index) {
-        return getList().listIterator(index);
-    }
-
-    @Override
-    public boolean remove(Object o) {
-        return getList().remove(o);
-    }
-
-    @Override
-    public Value remove(int index) {
-        return getList().remove(index);
-    }
-
-    @Override
-    public boolean removeAll(Collection<?> c) {
-        return getList().removeAll(c);
-    }
-
-    @Override
-    public boolean retainAll(Collection<?> c) {
-        return getList().retainAll(c);
-    }
-
-    @Override
-    public Value set(int index, Value element) {
-        checkElement(element);
-        return getList().set(index, element);
-    }
-
-    @Override
-    public int size() {
-        return getList().size();
-    }
-
-    @Override
-    public List<Value> subList(int fromIndex, int toIndex) {
-        return new ValueList(getList().subList(fromIndex, toIndex), type.getElementType());
-    }
-
-    @Override
-    public Object[] toArray() {
-        return getList().toArray();
-    }
-
-    @Override
-    public <Y> Y[] toArray(Y[] a) {
-        return getList().toArray(a);
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/ValueNull.java b/src/pl/edu/mimuw/cloudatlas/model/ValueNull.java
deleted file mode 100644
index c628beb..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/ValueNull.java
+++ /dev/null
@@ -1,155 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import pl.edu.mimuw.cloudatlas.model.Value;
-import pl.edu.mimuw.cloudatlas.model.ValueNull;
-
-/**
- * A special null value of an unknown type. This class is a singleton.
- *
- * @see TypePrimitve#NULL
- * @see Type#isCompatible(Value)
- */
-public class ValueNull extends Value {
-    private static ValueNull instance = null;
-
-    private ValueNull() {}
-
-    /**
-     * Gets a singleton instance of the <code>ValueNull</code> class. Every call to this method returns the same
-     * reference.
-     *
-     * @return an instance of <code>ValueNull</code>
-     */
-    public static ValueNull getInstance() {
-        if(instance == null)
-            instance = new ValueNull();
-        return instance;
-    }
-
-    @Override
-    public Value getDefaultValue() {
-        return instance;
-    }
-
-    @Override
-    public Value convertTo(Type type) {
-        switch(type.getPrimaryType()) {
-            case STRING:
-                return ValueString.NULL_STRING;
-            default:
-                return this;
-        }
-    }
-
-    @Override
-    public Type getType() {
-        return TypePrimitive.NULL;
-    }
-
-    @Override
-    public boolean isNull() {
-        return true;
-    }
-
-    @Override
-    public Value isEqual(Value value) {
-        return new ValueBoolean(isNull() && value.isNull());
-    }
-
-    @Override
-    public Value isLowerThan(Value value) {
-        if(value == getInstance())
-            return this;
-        return value.isLowerThan(this);
-    }
-
-    @Override
-    public Value addValue(Value value) {
-        if(value == getInstance())
-            return this;
-        return value.addValue(this);
-    }
-
-    @Override
-    public Value subtract(Value value) {
-        if(value == getInstance())
-            return this;
-        return value.subtract(this);
-    }
-
-    @Override
-    public Value multiply(Value value) {
-        if(value == getInstance())
-            return this;
-        return value.multiply(this);
-    }
-
-    @Override
-    public Value divide(Value value) {
-        if(value == getInstance())
-            return this;
-        return value.divide(this);
-    }
-
-    @Override
-    public Value modulo(Value value) {
-        if(value == getInstance())
-            return this;
-        return value.modulo(this);
-    }
-
-    @Override
-    public Value and(Value value) {
-        if(value == getInstance())
-            return this;
-        return value.and(this);
-    }
-
-    @Override
-    public Value or(Value value) {
-        if(value == getInstance())
-            return this;
-        return value.or(this);
-    }
-
-    @Override
-    public Value regExpr(Value value) {
-        if(value == getInstance())
-            return this;
-        return value.regExpr(this);
-    }
-
-    @Override
-    public Value negate() {
-        return this;
-    }
-
-    @Override
-    public Value valueSize() {
-        return this;
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/ValueSet.java b/src/pl/edu/mimuw/cloudatlas/model/ValueSet.java
deleted file mode 100644
index 9843cd4..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/ValueSet.java
+++ /dev/null
@@ -1,232 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.HashSet;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Set;
-
-import pl.edu.mimuw.cloudatlas.model.TypeCollection;
-import pl.edu.mimuw.cloudatlas.model.Value;
-import pl.edu.mimuw.cloudatlas.model.ValueSet;
-
-/**
- * A value representing a set of values of the specified type. Implements <code>Set</code> interface.
- * <p>
- * All constructors take a type of elements stored in this set. This type is checked when adding elements to the set and
- * an <code>IllegalArgumentException</code> is thrown in case of a mismatch.
- *
- * @see java.util.Set
- */
-public class ValueSet extends ValueSimple<Set<Value>> implements Set<Value> {
-    private TypeCollection type;
-
-    /**
-     * Creates a new <code>ValueSet</code> containing all the elements in the specified set.
-     *
-     * @param value a set which content will be copied to this value
-     * @param elementType type of elements stored in this set
-     */
-    public ValueSet(Set<Value> value, Type elementType) {
-        this(elementType);
-        if(value != null)
-            setValue(value);
-    }
-
-    /**
-     * Creates an empty set.
-     *
-     * @param elementType type of elements stored in this set
-     */
-    public ValueSet(Type elementType) {
-        super(new HashSet<Value>());
-        type = new TypeCollection(Type.PrimaryType.SET, elementType);
-    }
-
-    @Override
-    public Type getType() {
-        return type;
-    }
-
-    @Override
-    public Value getDefaultValue() {
-        return new ValueSet(((TypeCollection)this.getType()).getElementType());
-    }
-
-    /**
-     * Gets a <code>Set</code> containing all the objects stored in this value. Modifying the returned list will cause an
-     * exception.
-     */
-    @Override
-    public Set<Value> getValue() {
-        return getSet() == null? null : Collections.unmodifiableSet(getSet());
-    }
-
-    @Override
-    public ValueSet addValue(Value value) {
-        sameTypesOrThrow(value, Operation.ADD);
-        if(isNull() || value.isNull())
-            return new ValueSet(null, ((TypeCollection)getType()).getElementType());
-        Set<Value> result = new HashSet<Value>(getValue());
-        result.addAll(((ValueSet)value).getValue());
-        return new ValueSet(result, ((TypeCollection)getType()).getElementType());
-    }
-
-    @Override
-    public ValueInt valueSize() {
-        return new ValueInt((getSet() == null? null : (long)getSet().size()));
-    }
-
-    @Override
-    public void setValue(Set<Value> set) {
-        if(set == null)
-            super.setValue(null);
-        else {
-            super.setValue(new HashSet<Value>());
-            for(Value e : set)
-                add(e);
-        }
-    }
-
-    private Set<Value> getSet() {
-        return super.getValue();
-    }
-
-    private void checkElement(Value element) {
-        if(element == null)
-            throw new IllegalArgumentException("If you want to use null, create an object containing null instead.");
-        if(!type.getElementType().isCompatible(element.getType()))
-            throw new IllegalArgumentException("This set contains elements of type " + type.getElementType().toString()
-                    + " only. Incompatible with elements of type: " + element.getType().toString());
-    }
-
-    @Override
-    public boolean add(Value e) {
-        checkElement(e);
-        return getSet().add(e);
-    }
-
-    @Override
-    public boolean addAll(Collection<? extends Value> c) {
-        for(Value e : c)
-            checkElement(e);
-        return getSet().addAll(c);
-    }
-
-    @Override
-    public void clear() {
-        getSet().clear();
-    }
-
-    @Override
-    public boolean contains(Object o) {
-        return getSet().contains(o);
-    }
-
-    @Override
-    public boolean containsAll(Collection<?> c) {
-        return getSet().containsAll(c);
-    }
-
-    @Override
-    public boolean isEmpty() {
-        return getSet().isEmpty();
-    }
-
-    @Override
-    public Iterator<Value> iterator() {
-        return getSet().iterator();
-    }
-
-    @Override
-    public boolean remove(Object o) {
-        return getSet().remove(o);
-    }
-
-    @Override
-    public boolean removeAll(Collection<?> c) {
-        return getSet().removeAll(c);
-    }
-
-    @Override
-    public boolean retainAll(Collection<?> c) {
-        return getSet().retainAll(c);
-    }
-
-    @Override
-    public int size() {
-        return getSet().size();
-    }
-
-    @Override
-    public Object[] toArray() {
-        return getSet().toArray();
-    }
-
-    @Override
-    public <U> U[] toArray(U[] a) {
-        return getSet().toArray(a);
-    }
-
-    @Override
-    public Value convertTo(Type type) {
-        switch(type.getPrimaryType()) {
-            case SET:
-                if(getType().isCompatible(type))
-                    return this;
-                throw new UnsupportedConversionException(getType(), type);
-            case LIST:
-                if(this.type.getElementType().isCompatible(((TypeCollection)type).getElementType())) {
-                    if(this.isNull())
-                        return new ValueList(null, this.type.getElementType());
-                    List<Value> list = new ArrayList<Value>();
-                    list.addAll(this);
-                    return new ValueList(list, this.type.getElementType());
-                }
-                throw new UnsupportedConversionException(getType(), type);
-            case STRING:
-                if(getValue() == null)
-                    return ValueString.NULL_STRING;
-                StringBuilder sb = new StringBuilder();
-                sb.append("{");
-                boolean notFirst = false;
-                for(Value v : getValue()) {
-                    if(notFirst) {
-                        sb.append(", ");
-                    } else
-                        notFirst = true;
-                    sb.append(v.toString());
-                }
-                sb.append("}");
-                return new ValueString(sb.toString());
-            default:
-                throw new UnsupportedConversionException(getType(), type);
-        }
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/ValueSimple.java b/src/pl/edu/mimuw/cloudatlas/model/ValueSimple.java
deleted file mode 100644
index 803510f..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/ValueSimple.java
+++ /dev/null
@@ -1,89 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-/**
- * Class for wrapping Java types into <code>Value</code> objects.
- * <p>
- * This class is immutable.
- *
- * @param <T> a wrapped type
- */
-abstract class ValueSimple<T> extends Value {
-    private T value;
-
-    /**
-     * Constructs a new <code>Value</code> wrapping the specified <code>value</code>.
-     *
-     * @param value the value to wrap
-     */
-    public ValueSimple(T value) {
-        setValue(value);
-    }
-
-    /**
-     * Returns a hash code value for this object. This is a hash code of underlying wrapped object.
-     *
-     * @return the hash code for this value
-     */
-    @Override
-    public int hashCode() {
-        return getValue().hashCode();
-    }
-
-    /**
-     * Gets a wrapped object.
-     *
-     * @return the wrapped value
-     */
-    public T getValue() {
-        return value;
-    }
-
-    /**
-     * Sets a wrapped value. This method is not public to ensure that the underlying value cannot be changed.
-     *
-     * @param value the value to set
-     */
-    void setValue(T value) {
-        this.value = value;
-    }
-
-    @Override
-    public boolean isNull() {
-        return value == null;
-    }
-
-    @SuppressWarnings("unchecked")
-    @Override
-    public Value isEqual(Value v) {
-        sameTypesOrThrow(v, Operation.EQUAL);
-        if(isNull() && v.isNull())
-            return new ValueBoolean(true);
-        else if(isNull() || v.isNull())
-            return new ValueBoolean(false);
-        return new ValueBoolean(value.equals(((ValueSimple<T>)v).getValue()));
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/ValueString.java b/src/pl/edu/mimuw/cloudatlas/model/ValueString.java
deleted file mode 100644
index 314c602..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/ValueString.java
+++ /dev/null
@@ -1,120 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import java.text.ParseException;
-
-import pl.edu.mimuw.cloudatlas.model.Value;
-import pl.edu.mimuw.cloudatlas.model.ValueString;
-
-/**
- * A class that wraps a Java <code>String</code> object.
- */
-public class ValueString extends ValueSimple<String> {
-    /**
-     * Result of converting values representing null to <code>ValueString</code>.
-     */
-    protected static final ValueString NULL_STRING = new ValueString("NULL");
-
-    /**
-     * Constructs a new <code>ValueString</code> object wrapping the specified <code>value</code>.
-     *
-     * @param value the value to wrap
-     */
-    public ValueString(String value) {
-        super(value);
-    }
-
-    @Override
-    public Type getType() {
-        return TypePrimitive.STRING;
-    }
-
-    @Override
-    public Value getDefaultValue() {
-        return new ValueString("");
-    }
-
-    @Override
-    public ValueBoolean isLowerThan(Value value) {
-        sameTypesOrThrow(value, Operation.COMPARE);
-        if(isNull() || value.isNull())
-            return new ValueBoolean(null);
-        return new ValueBoolean(getValue().compareTo(((ValueString)value).getValue()) < 0);
-    }
-
-    @Override
-    public ValueString addValue(Value value) {
-        sameTypesOrThrow(value, Operation.ADD);
-        if(isNull() || value.isNull())
-            return new ValueString(null);
-        return new ValueString(getValue().concat(((ValueString)value).getValue()));
-    }
-
-    @Override
-    public ValueBoolean regExpr(Value value) {
-        sameTypesOrThrow(value, Operation.REG_EXPR);
-        if(isNull() || value.isNull())
-            return new ValueBoolean(null);
-        return new ValueBoolean(getValue().matches(((ValueString)value).getValue()));
-    }
-
-    @Override
-    public Value convertTo(Type type) {
-        switch(type.getPrimaryType()) {
-            case BOOLEAN:
-                return new ValueBoolean(Boolean.parseBoolean(getValue()));
-            case DOUBLE:
-                try {
-                    return new ValueDouble(Double.parseDouble(getValue()));
-                } catch(NumberFormatException exception) {
-                    return new ValueDouble(null);
-                }
-            case DURATION:
-                return new ValueDuration(getValue());
-            case INT:
-                try {
-                    return new ValueInt(Long.parseLong(getValue()));
-                } catch(NumberFormatException exception) {
-                    return new ValueInt(null);
-                }
-            case STRING:
-                return getValue() == null? ValueString.NULL_STRING : this;
-            case TIME:
-                try {
-                    return new ValueTime(getValue());
-                } catch(ParseException exception) {
-                    return new ValueTime((Long)null);
-                }
-            default:
-                throw new UnsupportedConversionException(getType(), type);
-        }
-    }
-
-    @Override
-    public ValueInt valueSize() {
-        return new ValueInt(getValue() == null? null : (long)getValue().length());
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/ValueTime.java b/src/pl/edu/mimuw/cloudatlas/model/ValueTime.java
deleted file mode 100644
index 8dd04fc..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/ValueTime.java
+++ /dev/null
@@ -1,116 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import java.text.DateFormat;
-import java.text.ParseException;
-import java.text.SimpleDateFormat;
-
-import pl.edu.mimuw.cloudatlas.model.Value;
-import pl.edu.mimuw.cloudatlas.model.ValueTime;
-
-/**
- * A class representing a POSIX time in milliseconds. This is a simple wrapper of a Java <code>Long</code> object.
- */
-public class ValueTime extends ValueSimple<Long> {
-    /**
-     * A format string for constructing from or converting to a <code>String</code> object.
-     */
-    public static final DateFormat TIME_FORMAT = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss.SSS");
-
-    /**
-     * Constructs a new <code>ValueTime</code> object wrapping the specified value.
-     *
-     * @param value the POSIX time
-     */
-    public ValueTime(Long value) {
-        super(value);
-    }
-
-    @Override
-    public Type getType() {
-        return TypePrimitive.TIME;
-    }
-
-    @Override
-    public Value getDefaultValue() {
-        return new ValueTime(0l);
-    }
-
-    /**
-     * Constructs a new <code>ValueTime</code> object from its textual representation.
-     *
-     * @param time a time formatted according to {@link #TIME_FORMAT}
-     * @throws ParseException if the <code>time</code> is incorrect
-     * @see #TIME_FORMAT
-     */
-    public ValueTime(String time) throws ParseException {
-        this(TIME_FORMAT.parse(time).getTime());
-    }
-
-    @Override
-    public ValueBoolean isLowerThan(Value value) {
-        sameTypesOrThrow(value, Operation.COMPARE);
-        if(isNull() || value.isNull())
-            return new ValueBoolean(null);
-        return new ValueBoolean(getValue() < ((ValueTime)value).getValue());
-    }
-
-    @Override
-    public ValueTime addValue(Value value) {
-        if(!value.getType().isCompatible(TypePrimitive.DURATION))
-            throw new IncompatibleTypesException(getType(), value.getType(), Operation.ADD);
-        if(isNull() || value.isNull())
-            return new ValueTime((Long)null);
-        return new ValueTime(getValue() + ((ValueDuration)value).getValue());
-    }
-
-    @Override
-    public Value subtract(Value value) {
-        if(value.getType().isCompatible(TypePrimitive.DURATION)) {
-            if(isNull() || value.isNull())
-                return new ValueTime((Long)null);
-            return new ValueTime(getValue() - ((ValueDuration)value).getValue());
-        } else if(value.getType().isCompatible(TypePrimitive.TIME)) {
-            if(isNull() || value.isNull())
-                return new ValueTime((Long)null);
-            return new ValueDuration(getValue() - ((ValueTime)value).getValue());
-        }
-        throw new IncompatibleTypesException(getType(), value.getType(), Operation.SUBTRACT);
-
-    }
-
-    @Override
-    public Value convertTo(Type type) {
-        switch(type.getPrimaryType()) {
-            case STRING:
-                return getValue() == null? ValueString.NULL_STRING : new ValueString(TIME_FORMAT.format(getValue()));
-            case TIME:
-                return this;
-            default:
-                throw new UnsupportedConversionException(getType(), type);
-        }
-    }
-}
diff --git a/src/pl/edu/mimuw/cloudatlas/model/ZMI.java b/src/pl/edu/mimuw/cloudatlas/model/ZMI.java
deleted file mode 100644
index a6b78da..0000000
--- a/src/pl/edu/mimuw/cloudatlas/model/ZMI.java
+++ /dev/null
@@ -1,166 +0,0 @@
-/**
- * Copyright (c) 2014, University of Warsaw
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without modification, are permitted
- * provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright notice, this list of
- * conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
- * conditions and the following disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
- * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
- * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
- * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-package pl.edu.mimuw.cloudatlas.model;
-
-import java.io.PrintStream;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-import java.util.Map.Entry;
-
-/**
- * A zone management information object. This object is a single node in a zone hierarchy. It stores zone attributes as well as
- * references to its father and sons in the tree.
- */
-public class ZMI implements Cloneable {
-    private final AttributesMap attributes = new AttributesMap();
-
-    private final List<ZMI> sons = new ArrayList<ZMI>();
-    private ZMI father;
-
-    /**
-     * Creates a new ZMI with no father (the root zone) and empty sons list.
-     */
-    public ZMI() {
-        this(null);
-    }
-
-    /**
-     * Creates a new ZMI with the specified node as a father and empty sons list. This method does not perform any
-     * operation on <code>father</code>. In particular, setting this object <code>father</code>'s son must be done
-     * separately.
-     *
-     * @param father the father of this ZMI
-     * @see #addSon(ZMI)
-     */
-    public ZMI(ZMI father) {
-        this.father = father;
-    }
-
-    /**
-     * Gets the father of this ZMI.
-     *
-     * @return the father of this ZMI or <code>null</code> if this is the root zone
-     */
-    public ZMI getFather() {
-        return father;
-    }
-
-    /**
-     * Sets or changes the father of this ZMI in the tree. This method does not perform any operation on
-     * <code>father</code>. In particular, setting this object as <code>father</code>'s son must be done separately.
-     *
-     * @param father a new father for this ZMI
-     * @see #addSon(ZMI)
-     */
-    public void setFather(ZMI father) {
-        this.father = father;
-    }
-
-    /**
-     * Gets the list of sons of this ZMI. Modifying a value in the returned list will cause an exception.
-     *
-     * @return the list of sons
-     */
-    public List<ZMI> getSons() {
-        return Collections.unmodifiableList(sons);
-    }
-
-    /**
-     * Adds the specified ZMI to the list of sons of this ZMI. This method does not perform any operation on
-     * <code>son</code>. In particular, setting this object as <code>son</code>'s father must be done separately.
-     *
-     * @param son
-     * @see #ZMI(ZMI)
-     * @see #setFather(ZMI)
-     */
-    public void addSon(ZMI son) {
-        sons.add(son);
-    }
-
-    /**
-     * Removes the specified ZMI from the list of sons of this ZMI. This method does not perform any operation on
-     * <code>son</code>. In particular, its father remains unchanged.
-     *
-     * @param son
-     * @see #setFather(ZMI)
-     */
-    public void removeSon(ZMI son) {
-        sons.remove(son);
-    }
-
-    /**
-     * Gets a map of all the attributes stored in this ZMI.
-     *
-     * @return map of attributes
-     */
-    public AttributesMap getAttributes() {
-        return attributes;
-    }
-
-    /**
-     * Prints recursively in a prefix order (starting from this ZMI) a whole tree with all the attributes.
-     *
-     * @param stream a destination stream
-     * @see #toString()
-     */
-    public void printAttributes(PrintStream stream) {
-        for(Entry<Attribute, Value> entry : attributes)
-            stream.println(entry.getKey() + " : " + entry.getValue().getType() + " = " + entry.getValue());
-        System.out.println();
-        for(ZMI son : sons)
-            son.printAttributes(stream);
-    }
-
-    /**
-     * Creates an independent copy of a whole hierarchy. A returned ZMI has the same reference as father (but the
-     * father does not have a reference to it as a son). For the root zone, the copy is completely independent, since
-     * its father is <code>null</code>.
-     *
-     * @return a deep copy of this ZMI
-     */
-    @Override
-    public ZMI clone() {
-        ZMI result = new ZMI(father);
-        result.attributes.add(attributes.clone());
-        for(ZMI son : sons) {
-            ZMI sonClone = son.clone();
-            result.sons.add(sonClone);
-            sonClone.father = result;
-        }
-        return result;
-    }
-
-    /**
-     * Prints a textual representation of this ZMI. It contains only attributes of this node.
-     *
-     * @return a textual representation of this object
-     * @see #printAttributes(PrintStream)
-     */
-    @Override
-    public String toString() {
-        return attributes.toString();
-    }
-}