Attribute.java

/*
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 *    Attribute.java
 *    Copyright (C) 1999-2012 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.core;

import java.io.Serializable;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.Date;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.List;
import java.util.Properties;

/**
 * Class for handling an attribute. Once an attribute has been created, it can't
 * be changed.
 * <p>
 * 
 * The following attribute types are supported:
 * <ul>
 * <li>numeric: <br/>
 * This type of attribute represents a floating-point number.</li>
 * <li>nominal: <br/>
 * This type of attribute represents a fixed set of nominal values.</li>
 * <li>string: <br/>
 * This type of attribute represents a dynamically expanding set of nominal
 * values. Usually used in text classification.</li>
 * <li>date: <br/>
 * This type of attribute represents a date, internally represented as
 * floating-point number storing the milliseconds since January 1, 1970,
 * 00:00:00 GMT. The string representation of the date must be <a
 * href="http://www.iso.org/iso/en/prods-services/popstds/datesandtime.html"
 * target="_blank"> ISO-8601</a> compliant, the default is
 * <code>yyyy-MM-dd'T'HH:mm:ss</code>.</li>
 * <li>relational: <br/>
 * This type of attribute can contain other attributes and is, e.g., used for
 * representing Multi-Instance data. (Multi-Instance data consists of a nominal
 * attribute containing the bag-id, then a relational attribute with all the
 * attributes of the bag, and finally the class attribute.)</li>
 * </ul>
 * 
 * Typical usage (code from the main() method of this class):
 * <p>
 * 
 * <code>
 * ... <br>
 * 
 * // Create numeric attributes "length" and "weight" <br>
 * Attribute length = new Attribute("length"); <br>
 * Attribute weight = new Attribute("weight"); <br><br>
 * 
 * // Create list to hold nominal values "first", "second", "third" <br>
 * List<String> my_nominal_values = new ArrayList<String>(3); <br>
 * my_nominal_values.add("first"); <br>
 * my_nominal_values.add("second"); <br>
 * my_nominal_values.add("third"); <br><br>
 * 
 * // Create nominal attribute "position" <br>
 * Attribute position = new Attribute("position", my_nominal_values);<br>
 * 
 * ... <br>
 * </code>
 * <p>
 * 
 * @author Eibe Frank (eibe@cs.waikato.ac.nz)
 * @version $Revision$
 */
public class Attribute implements Copyable, Serializable, RevisionHandler {

  /** for serialization */
  static final long serialVersionUID = -742180568732916383L;

  /** Constant set for numeric attributes. */
  public static final int NUMERIC = 0;

  /** Constant set for nominal attributes. */
  public static final int NOMINAL = 1;

  /** Constant set for attributes with string values. */
  public static final int STRING = 2;

  /** Constant set for attributes with date values. */
  public static final int DATE = 3;

  /** Constant set for relation-valued attributes. */
  public static final int RELATIONAL = 4;

  /** Constant set for symbolic attributes. */
  public static final int ORDERING_SYMBOLIC = 0;

  /** Constant set for ordered attributes. */
  public static final int ORDERING_ORDERED = 1;

  /** Constant set for modulo-ordered attributes. */
  public static final int ORDERING_MODULO = 2;

  /** The keyword used to denote the start of an arff attribute declaration */
  public final static String ARFF_ATTRIBUTE = "@attribute";

  /** A keyword used to denote a numeric attribute */
  public final static String ARFF_ATTRIBUTE_INTEGER = "integer";

  /** A keyword used to denote a numeric attribute */
  public final static String ARFF_ATTRIBUTE_REAL = "real";

  /** A keyword used to denote a numeric attribute */
  public final static String ARFF_ATTRIBUTE_NUMERIC = "numeric";

  /** The keyword used to denote a string attribute */
  public final static String ARFF_ATTRIBUTE_STRING = "string";

  /** The keyword used to denote a date attribute */
  public final static String ARFF_ATTRIBUTE_DATE = "date";

  /** The keyword used to denote a relation-valued attribute */
  public final static String ARFF_ATTRIBUTE_RELATIONAL = "relational";

  /** The keyword used to denote the end of the declaration of a subrelation */
  public final static String ARFF_END_SUBRELATION = "@end";

  /** Strings longer than this will be stored compressed. */
  protected static final int STRING_COMPRESS_THRESHOLD = 200;

  /** The attribute's name. */
  protected final/* @ spec_public non_null @ */String m_Name;

  /** The attribute's type. */
  protected/* @ spec_public @ */int m_Type;
  /*
   * @ invariant m_Type == NUMERIC || m_Type == DATE || m_Type == STRING ||
   * m_Type == NOMINAL || m_Type == RELATIONAL;
   */

  /** The attribute info (null for numeric attributes) */
  protected AttributeInfo m_AttributeInfo;

  /** The attribute's index. */
  protected/* @ spec_public @ */int m_Index = -1;

  /** The attribute's weight. */
  protected double m_Weight = 1.0;

  /** The meta data for the attribute. */
  protected AttributeMetaInfo m_AttributeMetaInfo;

  /**
   * Constructor for a numeric attribute.
   * 
   * @param attributeName the name for the attribute
   */
  // @ requires attributeName != null;
  // @ ensures m_Name == attributeName;
  public Attribute(String attributeName) {

    this(attributeName, (ProtectedProperties)null);
  }

  /**
   * Constructor for a numeric attribute, where metadata is supplied.
   * 
   * @param attributeName the name for the attribute
   * @param metadata the attribute's properties
   */
  // @ requires attributeName != null;
  // @ requires metadata != null;
  // @ ensures m_Name == attributeName;
  public Attribute(String attributeName, ProtectedProperties metadata) {

    m_Name = attributeName;
    if (metadata != null) {
      m_AttributeMetaInfo = new AttributeMetaInfo(metadata, this);
    }
  }

  /**
   * Constructor for a numeric or string attribute. Provides an alternative
   * way for creating string attributes.
   *
   * @param attributeName the name for the attribute
   * @param createStringAttribute if true, a string attribute will be created, otherwise a numeric one.
   */
  // @ requires attributeName != null;
  // @ ensures m_Name == attributeName;
  public Attribute(String attributeName, boolean createStringAttribute) {

    this(attributeName, createStringAttribute, (ProtectedProperties)null);
  }

  /**
   * Constructor for a numeric or string attribute, where metadata is supplied. Provides an alternative
   * way for creating string attributes.
   *
   * @param attributeName the name for the attribute
   * @param createStringAttribute if true, a string attribute will be created, otherwise a numeric one.
   * @param metadata the attribute's properties
   */
  // @ requires attributeName != null;
  // @ requires metadata != null;
  // @ ensures m_Name == attributeName;
  public Attribute(String attributeName, boolean createStringAttribute, ProtectedProperties metadata) {

    m_Name = attributeName;
    if (createStringAttribute) {
      m_AttributeInfo = new NominalAttributeInfo((List<String>)null, attributeName);
      m_Type = STRING;
    }
    if (metadata != null) {
      m_AttributeMetaInfo = new AttributeMetaInfo(metadata, this);
    }
  }

  /**
   * Constructor for a date attribute.
   * 
   * @param attributeName the name for the attribute
   * @param dateFormat a string suitable for use with SimpleDateFormatter for
   *          parsing dates.
   */
  // @ requires attributeName != null;
  // @ requires dateFormat != null;
  // @ ensures m_Name == attributeName;
  public Attribute(String attributeName, String dateFormat) {

    this(attributeName, dateFormat, (ProtectedProperties)null);
  }

  /**
   * Constructor for a date attribute, where metadata is supplied.
   * 
   * @param attributeName the name for the attribute
   * @param dateFormat a string suitable for use with SimpleDateFormatter for
   *          parsing dates.
   * @param metadata the attribute's properties
   */
  // @ requires attributeName != null;
  // @ requires dateFormat != null;
  // @ requires metadata != null;
  // @ ensures m_Name == attributeName;
  public Attribute(String attributeName, String dateFormat,
    ProtectedProperties metadata) {

    m_Name = attributeName;
    m_Type = DATE;
    m_AttributeInfo = new DateAttributeInfo(dateFormat);
    if (metadata != null) {
      m_AttributeMetaInfo = new AttributeMetaInfo(metadata, this);
    }
  }

  /**
   * Constructor for nominal attributes and string attributes. If a null vector
   * of attribute values is passed to the method, the attribute is assumed to be
   * a string.
   * 
   * @param attributeName the name for the attribute
   * @param attributeValues a vector of strings denoting the attribute values.
   *          Null if the attribute is a string attribute.
   */
  // @ requires attributeName != null;
  // @ ensures m_Name == attributeName;
  public Attribute(String attributeName, List<String> attributeValues) {

    this(attributeName, attributeValues, (ProtectedProperties)null);
  }

  /**
   * Constructor for nominal attributes and string attributes, where metadata is
   * supplied. If a null vector of attribute values is passed to the method, the
   * attribute is assumed to be a string.
   * 
   * @param attributeName the name for the attribute
   * @param attributeValues a vector of strings denoting the attribute values.
   *          Null if the attribute is a string attribute.
   * @param metadata the attribute's properties
   */
  // @ requires attributeName != null;
  // @ requires metadata != null;
  /*
   * @ ensures m_Name == attributeName; ensures m_Index == -1; ensures
   * attributeValues == null && m_Type == STRING || attributeValues != null &&
   * m_Type == NOMINAL && m_Values.size() == attributeValues.size(); signals
   * (IllegalArgumentException ex) (* if duplicate strings in attributeValues
   * *);
   */
  public Attribute(String attributeName, List<String> attributeValues,
    ProtectedProperties metadata) {

    m_Name = attributeName;
    m_AttributeInfo = new NominalAttributeInfo(attributeValues, attributeName);
    if (attributeValues == null) {
      m_Type = STRING;
    } else {
      m_Type = NOMINAL;
    }
    if (metadata != null) {
      m_AttributeMetaInfo = new AttributeMetaInfo(metadata, this);
    }
  }

  /**
   * Constructor for relation-valued attributes.
   * 
   * @param attributeName the name for the attribute
   * @param header an Instances object specifying the header of the relation.
   */
  public Attribute(String attributeName, Instances header) {

    this(attributeName, header, (ProtectedProperties)null);
  }

  /**
   * Constructor for relation-valued attributes.
   * 
   * @param attributeName the name for the attribute
   * @param header an Instances object specifying the header of the relation.
   * @param metadata the attribute's properties
   */
  public Attribute(String attributeName, Instances header,
    ProtectedProperties metadata) {

    if (header.numInstances() > 0) {
      throw new IllegalArgumentException("Header for relation-valued "
        + "attribute should not contain " + "any instances");
    }
    m_Name = attributeName;
    m_Type = RELATIONAL;
    m_AttributeInfo = new RelationalAttributeInfo(header);
    if (metadata != null) {
      m_AttributeMetaInfo = new AttributeMetaInfo(metadata, this);
    }
  }

  /**
   * Produces a shallow copy of this attribute.
   * 
   * @return a copy of this attribute with the same index
   */
  // @ also ensures \result instanceof Attribute;
  @Override
  public/* @ pure non_null @ */Object copy() {

    return copy(m_Name);
  }

  /**
   * Returns an enumeration of all the attribute's values if the attribute is
   * nominal, string, or relation-valued, null otherwise.
   * 
   * @return enumeration of all the attribute's values
   */
  public final/* @ pure @ */Enumeration<Object> enumerateValues() {

    if (isNominal() || isString()) {
      final Enumeration<Object> ee = 
        new WekaEnumeration<Object>(((NominalAttributeInfo)m_AttributeInfo).m_Values);
      return new Enumeration<Object>() {
        @Override
        public boolean hasMoreElements() {
          return ee.hasMoreElements();
        }

        @Override
        public Object nextElement() {
          Object oo = ee.nextElement();
          if (oo instanceof SerializedObject) {
            return ((SerializedObject) oo).getObject();
          } else {
            return oo;
          }
        }
      };
    }
    return null;
  }

  /**
   * Tests if given attribute is equal to this attribute. Attribute indices are ignored in the comparison.
   * 
   * @param other the Object to be compared to this attribute
   * @return true if the given attribute is equal to this attribute
   */
  @Override
  public final/* @ pure @ */boolean equals(Object other) {
    return (equalsMsg(other) == null);
  }
  
  /**
   * Returns a hash code for this attribute based on its name.
   * 
   * @return the hash code
   */
  @Override
  public final/* @ pure @ */int hashCode() {
    return name().hashCode();
  }
  
  /**
   * Tests if given attribute is equal to this attribute. If they're not the
   * same a message detailing why they differ will be returned, otherwise null.
   * Attribute indices are ignored in the comparison.
   * 
   * @param other the Object to be compared to this attribute
   * @return null if the given attribute is equal to this attribute
   */
  public final String equalsMsg(Object other) {
    if (other == null) {
      return "Comparing with null object";
    }

    if (!(other.getClass().equals(this.getClass()))) {
      return "Object has wrong class";
    }

    Attribute att = (Attribute) other;
    if (!m_Name.equals(att.m_Name)) {
      return "Names differ: " + m_Name + " != " + att.m_Name;
    }

    if (isNominal() && att.isNominal()) {
      if (((NominalAttributeInfo)m_AttributeInfo).m_Values.size() != 
          ((NominalAttributeInfo)att.m_AttributeInfo).m_Values.size()) {
        return "Different number of labels: " + ((NominalAttributeInfo)m_AttributeInfo).m_Values.size() + " != "
          + ((NominalAttributeInfo)att.m_AttributeInfo).m_Values.size();
      }

      for (int i = 0; i < ((NominalAttributeInfo)m_AttributeInfo).m_Values.size(); i++) {
        if (!((NominalAttributeInfo)m_AttributeInfo).m_Values.get(i).
            equals(((NominalAttributeInfo)att.m_AttributeInfo).m_Values.get(i))) {
          return "Labels differ at position " + (i + 1) + ": "
            + ((NominalAttributeInfo)m_AttributeInfo).m_Values.get(i) + " != " + 
            ((NominalAttributeInfo)att.m_AttributeInfo).m_Values.get(i);
        }
      }

      return null;
    }

    if (isRelationValued() && att.isRelationValued()) {
      return ((RelationalAttributeInfo)m_AttributeInfo).m_Header.equalHeadersMsg(((RelationalAttributeInfo)att.m_AttributeInfo).m_Header);
    }

    if ((type() != att.type())) {
      return "Types differ: " + typeToString(this) + " != " + typeToString(att);
    }

    return null;
  }

  /**
   * Returns a string representation of the attribute type.
   * 
   * @param att the attribute to return the type string for
   * @return the string representation of the attribute type
   */
  public static String typeToString(Attribute att) {
    return typeToString(att.type());
  }

  /**
   * Returns a string representation of the attribute type.
   * 
   * @param type the type of the attribute
   * @return the string representation of the attribute type
   */
  public static String typeToString(int type) {
    String result;

    switch (type) {
    case NUMERIC:
      result = "numeric";
      break;

    case NOMINAL:
      result = "nominal";
      break;

    case STRING:
      result = "string";
      break;

    case DATE:
      result = "date";
      break;

    case RELATIONAL:
      result = "relational";
      break;

    default:
      result = "unknown(" + type + ")";
    }

    return result;
  }

  /**
   * Returns a short string representation of the attribute type.
   * 
   * @param att the attribute to return the type string for
   * @return the string representation of the attribute type
   */
  public static String typeToStringShort(Attribute att) {
    return typeToStringShort(att.type());
  }

  /**
   * Returns a short string representation of the attribute type.
   * 
   * @param type the type of the attribute
   * @return the string representation of the attribute type
   */
  public static String typeToStringShort(int type) {
    String result;

    switch (type) {
    case NUMERIC:
      result = "Num";
      break;

    case NOMINAL:
      result = "Nom";
      break;

    case STRING:
      result = "Str";
      break;

    case DATE:
      result = "Dat";
      break;

    case RELATIONAL:
      result = "Rel";
      break;

    default:
      result = "???";
    }

    return result;
  }

  /**
   * Returns the index of this attribute.
   * 
   * @return the index of this attribute
   */
  // @ ensures \result == m_Index;
  public final/* @ pure @ */int index() {

    return m_Index;
  }

  /**
   * Returns the index of a given attribute value. (The index of the first
   * occurence of this value.)
   * 
   * @param value the value for which the index is to be returned
   * @return the index of the given attribute value if attribute is nominal or a
   *         string, -1 if it is not or the value can't be found
   */
  public final int indexOfValue(String value) {

    if (!isNominal() && !isString()) {
      return -1;
    }
    Object store = value;
    if (value.length() > STRING_COMPRESS_THRESHOLD) {
      try {
        store = new SerializedObject(value, true);
      } catch (Exception ex) {
        System.err.println("Couldn't compress string attribute value -"
          + " searching uncompressed.");
      }
    }
    Integer val = ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.get(store);
    if (val == null) {
      return -1;
    } else {
      return val.intValue();
    }
  }

  /**
   * Test if the attribute is nominal.
   * 
   * @return true if the attribute is nominal
   */
  // @ ensures \result <==> (m_Type == NOMINAL);
  public final/* @ pure @ */boolean isNominal() {

    return (m_Type == NOMINAL);
  }

  /**
   * Tests if the attribute is numeric.
   * 
   * @return true if the attribute is numeric
   */
  // @ ensures \result <==> ((m_Type == NUMERIC) || (m_Type == DATE));
  public final/* @ pure @ */boolean isNumeric() {

    return ((m_Type == NUMERIC) || (m_Type == DATE));
  }

  /**
   * Tests if the attribute is relation valued.
   * 
   * @return true if the attribute is relation valued
   */
  // @ ensures \result <==> (m_Type == RELATIONAL);
  public final/* @ pure @ */boolean isRelationValued() {

    return (m_Type == RELATIONAL);
  }

  /**
   * Tests if the attribute is a string.
   * 
   * @return true if the attribute is a string
   */
  // @ ensures \result <==> (m_Type == STRING);
  public final/* @ pure @ */boolean isString() {

    return (m_Type == STRING);
  }

  /**
   * Tests if the attribute is a date type.
   * 
   * @return true if the attribute is a date type
   */
  // @ ensures \result <==> (m_Type == DATE);
  public final/* @ pure @ */boolean isDate() {

    return (m_Type == DATE);
  }

  /**
   * Returns the attribute's name.
   * 
   * @return the attribute's name as a string
   */
  // @ ensures \result == m_Name;
  public final/* @ pure @ */String name() {

    return m_Name;
  }

  /**
   * Returns the number of attribute values. Returns 0 for attributes that are
   * not either nominal, string, or relation-valued.
   * 
   * @return the number of attribute values
   */
  public final/* @ pure @ */int numValues() {

    if (!isNominal() && !isString() && !isRelationValued()) {
      return 0;
    } else {
      return ((NominalAttributeInfo)m_AttributeInfo).m_Values.size();
    }
  }

  /**
   * Returns a description of this attribute in ARFF format. Quotes strings if
   * they contain whitespace characters, or if they are a question mark.
   * 
   * @return a description of this attribute as a string
   */
  @Override
  public final String toString() {

    StringBuffer text = new StringBuffer();

    text.append(ARFF_ATTRIBUTE).append(" ").append(Utils.quote(m_Name))
      .append(" ");
    switch (m_Type) {
    case NOMINAL:
      text.append('{');
      Enumeration<Object> enu = enumerateValues();
      while (enu.hasMoreElements()) {
        text.append(Utils.quote((String) enu.nextElement()));
        if (enu.hasMoreElements()) {
          text.append(',');
        }
      }
      text.append('}');
      text.append((weight() != 1.0) ? " {" + weight() + "}" : "");
      break;
    case NUMERIC:
      text.append(ARFF_ATTRIBUTE_NUMERIC);
      text.append((weight() != 1.0) ?  " {" + weight() + "}" : "");
      break;
    case STRING:
      text.append(ARFF_ATTRIBUTE_STRING);
      text.append((weight() != 1.0) ?  " {" + weight() + "}" : "");
      break;
    case DATE:
      text.append(ARFF_ATTRIBUTE_DATE).append(" ")
        .append(Utils.quote(((DateAttributeInfo)m_AttributeInfo).m_DateFormat.toPattern()));
      text.append((weight() != 1.0) ?  " {" + weight() + "}" : "");
      break;
    case RELATIONAL:
      text.append(ARFF_ATTRIBUTE_RELATIONAL);
      text.append((weight() != 1.0) ?  " {" + weight() + "}" : "");
      text.append("\n");
      Enumeration<Attribute> enm = ((RelationalAttributeInfo)m_AttributeInfo).m_Header.enumerateAttributes();
      while (enm.hasMoreElements()) {
        text.append(enm.nextElement()).append("\n");
      }
      text.append(ARFF_END_SUBRELATION).append(" ").append(Utils.quote(m_Name));
      break;
    default:
      text.append("UNKNOWN");
      break;
    }
    return text.toString();
  }

  /**
   * Returns the attribute's type as an integer.
   * 
   * @return the attribute's type.
   */
  // @ ensures \result == m_Type;
  public final/* @ pure @ */int type() {

    return m_Type;
  }

  /**
   * Returns the Date format pattern in case this attribute is of type DATE,
   * otherwise an empty string.
   * 
   * @return the date format pattern
   * @see java.text.SimpleDateFormat
   */
  public final String getDateFormat() {
    if (isDate()) {
      return ((DateAttributeInfo)m_AttributeInfo).m_DateFormat.toPattern();
    } else {
      return "";
    }
  }

  /**
   * Returns a value of a nominal or string attribute. Returns an empty string
   * if the attribute is neither a string nor a nominal attribute.
   * 
   * @param valIndex the value's index
   * @return the attribute's value as a string
   */
  public final/* @ non_null pure @ */String value(int valIndex) {

    if (!isNominal() && !isString()) {
      return "";
    } else {
      Object val = ((NominalAttributeInfo)m_AttributeInfo).m_Values.get(valIndex);

      // If we're storing strings compressed, uncompress it.
      if (val instanceof SerializedObject) {
        val = ((SerializedObject) val).getObject();
      }
      return (String) val;
    }
  }

  /**
   * Returns the header info for a relation-valued attribute, null if the
   * attribute is not relation-valued.
   * 
   * @return the attribute's value as an Instances object
   */
  public final/* @ non_null pure @ */Instances relation() {

    if (!isRelationValued()) {
      return null;
    } else {
      return ((RelationalAttributeInfo)m_AttributeInfo).m_Header;
    }
  }

  /**
   * Returns a value of a relation-valued attribute. Returns null if the
   * attribute is not relation-valued.
   * 
   * @param valIndex the value's index
   * @return the attribute's value as an Instances object
   */
  public final/* @ non_null pure @ */Instances relation(int valIndex) {

    if (!isRelationValued()) {
      return null;
    } else {
      return (Instances) ((RelationalAttributeInfo)m_AttributeInfo).m_Values.get(valIndex);
    }
  }

  /**
   * Constructor for a numeric attribute with a particular index.
   * 
   * @param attributeName the name for the attribute
   * @param index the attribute's index
   */
  // @ requires attributeName != null;
  // @ requires index >= 0;
  // @ ensures m_Name == attributeName;
  // @ ensures m_Index == index;
  public Attribute(String attributeName, int index) {

    this(attributeName);
    m_Index = index;
  }

  /**
   * Constructor for date attributes with a particular index.
   * 
   * @param attributeName the name for the attribute
   * @param dateFormat a string suitable for use with SimpleDateFormatter for
   *          parsing dates. Null for a default format string.
   * @param index the attribute's index
   */
  // @ requires attributeName != null;
  // @ requires index >= 0;
  // @ ensures m_Name == attributeName;
  // @ ensures m_Index == index;
  public Attribute(String attributeName, String dateFormat, int index) {

    this(attributeName, dateFormat);
    m_Index = index;
  }

  /**
   * Constructor for nominal attributes and string attributes with a particular
   * index. If a null vector of attribute values is passed to the method, the
   * attribute is assumed to be a string.
   * 
   * @param attributeName the name for the attribute
   * @param attributeValues a vector of strings denoting the attribute values.
   *          Null if the attribute is a string attribute.
   * @param index the attribute's index
   */
  // @ requires attributeName != null;
  // @ requires index >= 0;
  // @ ensures m_Name == attributeName;
  // @ ensures m_Index == index;
  public Attribute(String attributeName, List<String> attributeValues, int index) {

    this(attributeName, attributeValues);
    m_Index = index;
  }

  /**
   * Constructor for a relation-valued attribute with a particular index.
   * 
   * @param attributeName the name for the attribute
   * @param header the header information for this attribute
   * @param index the attribute's index
   */
  // @ requires attributeName != null;
  // @ requires index >= 0;
  // @ ensures m_Name == attributeName;
  // @ ensures m_Index == index;
  public Attribute(String attributeName, Instances header, int index) {

    this(attributeName, header);
    m_Index = index;
  }

  /**
   * Adds a string value to the list of valid strings for attributes of type
   * STRING and returns the index of the string.
   * 
   * @param value The string value to add
   * @return the index assigned to the string, or -1 if the attribute is not of
   *         type Attribute.STRING
   */
  /*
   * @ requires value != null; ensures isString() && 0 <= \result && \result <
   * m_Values.size() || ! isString() && \result == -1;
   */
  public int addStringValue(String value) {

    if (!isString()) {
      return -1;
    }
    Object store = value;

    if (value.length() > STRING_COMPRESS_THRESHOLD) {
      try {
        store = new SerializedObject(value, true);
      } catch (Exception ex) {
        System.err.println("Couldn't compress string attribute value -"
          + " storing uncompressed.");
      }
    }
    Integer index = ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.get(store);
    if (index != null) {
      return index.intValue();
    } else {
      int intIndex = ((NominalAttributeInfo)m_AttributeInfo).m_Values.size();
      ((NominalAttributeInfo)m_AttributeInfo).m_Values.add(store);
      ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.put(store, new Integer(intIndex));
      return intIndex;
    }
  }

  /**
   * Clear the map and list of values and set them to contain just the supplied
   * value
   * 
   * @param value the current (and only) value of this String attribute. If null
   * then just the map is cleared.
   */
  public void setStringValue(String value) {
    if (!isString()) {
      return;
    }

    ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.clear();
    ((NominalAttributeInfo)m_AttributeInfo).m_Values.clear();
    if (value != null) {
      addStringValue(value);
    }
  }

  /**
   * Adds a string value to the list of valid strings for attributes of type
   * STRING and returns the index of the string. This method is more efficient
   * than addStringValue(String) for long strings.
   * 
   * @param src The Attribute containing the string value to add.
   * @param index the index of the string value in the source attribute.
   * @return the index assigned to the string, or -1 if the attribute is not of
   *         type Attribute.STRING
   */
  /*
   * @ requires src != null; requires 0 <= index && index < src.m_Values.size();
   * ensures isString() && 0 <= \result && \result < m_Values.size() || !
   * isString() && \result == -1;
   */
  public int addStringValue(Attribute src, int index) {

    if (!isString()) {
      return -1;
    }
    Object store = ((NominalAttributeInfo)src.m_AttributeInfo).m_Values.get(index);
    Integer oldIndex = ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.get(store);
    if (oldIndex != null) {
      return oldIndex.intValue();
    } else {
      int intIndex = ((NominalAttributeInfo)m_AttributeInfo).m_Values.size();
      ((NominalAttributeInfo)m_AttributeInfo).m_Values.add(store);
      ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.put(store, new Integer(intIndex));
      return intIndex;
    }
  }

  /**
   * Adds a relation to a relation-valued attribute.
   * 
   * @param value The value to add
   * @return the index assigned to the value, or -1 if the attribute is not of
   *         type Attribute.RELATIONAL
   */
  public int addRelation(Instances value) {

    if (!isRelationValued()) {
      return -1;
    }
    if (!((RelationalAttributeInfo)m_AttributeInfo).m_Header.equalHeaders(value)) {
      throw new IllegalArgumentException("Incompatible value for "
        + "relation-valued attribute.\n" + ((RelationalAttributeInfo)m_AttributeInfo).m_Header.equalHeadersMsg(value));
    }
    Integer index = ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.get(value);
    if (index != null) {
      return index.intValue();
    } else {
      int intIndex = ((NominalAttributeInfo)m_AttributeInfo).m_Values.size();
      ((NominalAttributeInfo)m_AttributeInfo).m_Values.add(value);
      ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.put(value, new Integer(intIndex));
      return intIndex;
    }
  }

  /**
   * Adds an attribute value. Creates a fresh list of attribute values before
   * adding it.
   * 
   * @param value the attribute value
   */
  final void addValue(String value) {

    ((NominalAttributeInfo)m_AttributeInfo).m_Values = 
      Utils.cast(((NominalAttributeInfo)m_AttributeInfo).m_Values.clone());
    ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable = 
      Utils.cast(((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.clone());
    forceAddValue(value);
  }

  /**
   * Produces a shallow copy of this attribute with a new name.
   * 
   * @param newName the name of the new attribute
   * @return a copy of this attribute with the same index
   */
  // @ requires newName != null;
  // @ ensures \result.m_Name == newName;
  // @ ensures \result.m_Index == m_Index;
  // @ ensures \result.m_Type == m_Type;
  public final/* @ pure non_null @ */Attribute copy(String newName) {

    Attribute copy = new Attribute(newName);

    copy.m_Index = m_Index;
    copy.m_Type = m_Type;
    copy.m_AttributeInfo = m_AttributeInfo;
    copy.m_AttributeMetaInfo = m_AttributeMetaInfo;
    copy.m_Weight = m_Weight;

    return copy;
  }

  /**
   * Removes a value of a nominal, string, or relation-valued attribute. Creates
   * a fresh list of attribute values before removing it.
   * 
   * @param index the value's index
   * @throws IllegalArgumentException if the attribute is not of the correct
   *           type
   */
  // @ requires isNominal() || isString() || isRelationValued();
  // @ requires 0 <= index && index < m_Values.size();
  final void delete(int index) {

    if (!isNominal() && !isString() && !isRelationValued()) {
      throw new IllegalArgumentException("Can only remove value of "
        + "nominal, string or relation-" + " valued attribute!");
    } else {
      ((NominalAttributeInfo)m_AttributeInfo).m_Values = 
        Utils.cast(((NominalAttributeInfo)m_AttributeInfo).m_Values.clone());
      ((NominalAttributeInfo)m_AttributeInfo).m_Values.remove(index);
      if (!isRelationValued()) {
        Hashtable<Object, Integer> hash = new Hashtable<Object, Integer>(
          ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.size());
        Enumeration<Object> enu = ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.keys();
        while (enu.hasMoreElements()) {
          Object string = enu.nextElement();
          Integer valIndexObject = ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.get(string);
          int valIndex = valIndexObject.intValue();
          if (valIndex > index) {
            hash.put(string, new Integer(valIndex - 1));
          } else if (valIndex < index) {
            hash.put(string, valIndexObject);
          }
        }
        ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable = hash;
      }
    }
  }

  /**
   * Adds an attribute value.
   * 
   * @param value the attribute value
   */
  // @ requires value != null;
  // @ ensures m_Values.size() == \old(m_Values.size()) + 1;
  final void forceAddValue(String value) {

    Object store = value;
    if (value.length() > STRING_COMPRESS_THRESHOLD) {
      try {
        store = new SerializedObject(value, true);
      } catch (Exception ex) {
        System.err.println("Couldn't compress string attribute value -"
          + " storing uncompressed.");
      }
    }
    ((NominalAttributeInfo)m_AttributeInfo).m_Values.add(store);
    ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.
      put(store, new Integer(((NominalAttributeInfo)m_AttributeInfo).m_Values.size() - 1));
  }

  /**
   * Sets the index of this attribute.
   * 
   * @param index the index of this attribute
   */
  // @ requires 0 <= index;
  // @ assignable m_Index;
  // @ ensures m_Index == index;
  final void setIndex(int index) {

    m_Index = index;
  }

  /**
   * Sets a value of a nominal attribute or string attribute. Creates a fresh
   * list of attribute values before it is set.
   * 
   * @param index the value's index
   * @param string the value
   * @throws IllegalArgumentException if the attribute is not nominal or string.
   */
  // @ requires string != null;
  // @ requires isNominal() || isString();
  // @ requires 0 <= index && index < m_Values.size();
  final void setValue(int index, String string) {

    switch (m_Type) {
    case NOMINAL:
    case STRING:
      ((NominalAttributeInfo)m_AttributeInfo).m_Values = 
        Utils.cast(((NominalAttributeInfo)m_AttributeInfo).m_Values.clone());
      ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable = 
        Utils.cast(((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.clone());
      Object store = string;
      if (string.length() > STRING_COMPRESS_THRESHOLD) {
        try {
          store = new SerializedObject(string, true);
        } catch (Exception ex) {
          System.err.println("Couldn't compress string attribute value -"
            + " storing uncompressed.");
        }
      }
      ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.
        remove(((NominalAttributeInfo)m_AttributeInfo).m_Values.get(index));
      ((NominalAttributeInfo)m_AttributeInfo).m_Values.set(index, store);
      ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.put(store, new Integer(index));
      break;
    default:
      throw new IllegalArgumentException("Can only set values for nominal"
        + " or string attributes!");
    }
  }

  /**
   * Sets a value of a relation-valued attribute. Creates a fresh list of
   * attribute values before it is set.
   * 
   * @param index the value's index
   * @param data the value
   * @throws IllegalArgumentException if the attribute is not relation-valued.
   */
  final void setValue(int index, Instances data) {

    if (isRelationValued()) {
      if (!data.equalHeaders(((RelationalAttributeInfo)m_AttributeInfo).m_Header)) {
        throw new IllegalArgumentException("Can't set relational value. "
          + "Headers not compatible.\n" + data.equalHeadersMsg(((RelationalAttributeInfo)m_AttributeInfo).m_Header));
      }
      ((NominalAttributeInfo)m_AttributeInfo).m_Values = 
        Utils.cast(((NominalAttributeInfo)m_AttributeInfo).m_Values.clone());
      ((NominalAttributeInfo)m_AttributeInfo).m_Values.set(index, data);
    } else {
      throw new IllegalArgumentException("Can only set value for"
        + " relation-valued attributes!");
    }
  }

  /**
   * Returns the given amount of milliseconds formatted according to the current
   * Date format.
   * 
   * @param date the date, represented in milliseconds since January 1, 1970,
   *          00:00:00 GMT, to return as string
   * @return the formatted date
   */
  // @ requires isDate();
  public/* @pure@ */String formatDate(double date) {
    switch (m_Type) {
    case DATE:
      return ((DateAttributeInfo)m_AttributeInfo).m_DateFormat.format(new Date((long) date));
    default:
      throw new IllegalArgumentException("Can only format date values for date"
        + " attributes!");
    }
  }

  /**
   * Parses the given String as Date, according to the current format and
   * returns the corresponding amount of milliseconds.
   * 
   * @param string the date to parse
   * @return the date in milliseconds since January 1, 1970, 00:00:00 GMT
   * @throws ParseException if parsing fails
   */
  // @ requires isDate();
  // @ requires string != null;
  public double parseDate(String string) throws ParseException {
    switch (m_Type) {
    case DATE:
      long time = ((DateAttributeInfo)m_AttributeInfo).m_DateFormat.parse(string).getTime();
      // TODO put in a safety check here if we can't store the value in a
      // double.
      return time;
    default:
      throw new IllegalArgumentException("Can only parse date values for date"
        + " attributes!");
    }
  }

  /**
   * Returns the properties supplied for this attribute. Returns null
   * if there is no meta data for this attribute.
   * 
   * @return metadata for this attribute
   */
  public final/* @ pure @ */ProtectedProperties getMetadata() {

    if (m_AttributeMetaInfo == null) {
      return null;
    }
    return m_AttributeMetaInfo.m_Metadata;
  }

  /**
   * Returns the ordering of the attribute. One of the following:
   * 
   * ORDERING_SYMBOLIC - attribute values should be treated as symbols.
   * ORDERING_ORDERED - attribute values have a global ordering. ORDERING_MODULO
   * - attribute values have an ordering which wraps.
   * 
   * @return the ordering type of the attribute
   */
  public final/* @ pure @ */int ordering() {

    if (m_AttributeMetaInfo == null) {
      return ORDERING_ORDERED;
    }
    return m_AttributeMetaInfo.m_Ordering;
  }

  /**
   * Returns whether the attribute values are equally spaced.
   * 
   * @return whether the attribute is regular or not
   */
  public final/* @ pure @ */boolean isRegular() {

    if (m_AttributeMetaInfo == null) {
      return true;
    }
    return m_AttributeMetaInfo.m_IsRegular;
  }

  /**
   * Returns whether the attribute can be averaged meaningfully.
   * 
   * @return whether the attribute can be averaged or not
   */
  public final/* @ pure @ */boolean isAveragable() {

    if (m_AttributeMetaInfo == null) {
      return true;
    }
    return m_AttributeMetaInfo.m_IsAveragable;
  }

  /**
   * Returns whether the attribute has a zeropoint and may be added
   * meaningfully.
   * 
   * @return whether the attribute has a zeropoint or not
   */
  public final/* @ pure @ */boolean hasZeropoint() {

    if (m_AttributeMetaInfo == null) {
      return true;
    }
    return m_AttributeMetaInfo.m_HasZeropoint;
  }

  /**
   * Returns the attribute's weight.
   * 
   * @return the attribute's weight as a double
   */
  public final/* @ pure @ */double weight() {

    return m_Weight;
  }

  /**
   * Sets the new attribute's weight. Does not modify the weight info stored in the
   * attribute's meta data object!
   * 
   * @param value the new weight
   */
  public void setWeight(double value) {

    m_Weight = value;
  }

  /**
   * Returns the lower bound of a numeric attribute.
   * 
   * @return the lower bound of the specified numeric range
   */
  public final/* @ pure @ */double getLowerNumericBound() {

    if (m_AttributeMetaInfo == null) {
      return -Double.MAX_VALUE;
    }
    return m_AttributeMetaInfo.m_LowerBound;
  }

  /**
   * Returns whether the lower numeric bound of the attribute is open.
   * 
   * @return whether the lower numeric bound is open or not (closed)
   */
  public final/* @ pure @ */boolean lowerNumericBoundIsOpen() {

    if (m_AttributeMetaInfo == null) {
      return true;
    }
    return m_AttributeMetaInfo.m_LowerBoundIsOpen;
  }

  /**
   * Returns the upper bound of a numeric attribute.
   * 
   * @return the upper bound of the specified numeric range
   */
  public final/* @ pure @ */double getUpperNumericBound() {

    if (m_AttributeMetaInfo == null) {
      return Double.MAX_VALUE;
    }
    return m_AttributeMetaInfo.m_UpperBound;
  }

  /**
   * Returns whether the upper numeric bound of the attribute is open.
   * 
   * @return whether the upper numeric bound is open or not (closed)
   */
  public final/* @ pure @ */boolean upperNumericBoundIsOpen() {

    if (m_AttributeMetaInfo == null) {
      return true;
    }
    return m_AttributeMetaInfo.m_UpperBoundIsOpen;
  }

  /**
   * Determines whether a value lies within the bounds of the attribute.
   * 
   * @param value the value to check
   * @return whether the value is in range
   */
  public final/* @ pure @ */boolean isInRange(double value) {

    // dates and missing values are a special case
    if (m_Type == DATE || Utils.isMissingValue(value)) {
      return true;
    }
    if (m_Type != NUMERIC) {
      // do label range check
      int intVal = (int) value;
      if (intVal < 0 || intVal >= ((NominalAttributeInfo)m_AttributeInfo).m_Hashtable.size()) {
        return false;
      }
    } else {
      if (m_AttributeMetaInfo == null) {
        return true;
      }
      // do numeric bounds check
      if (m_AttributeMetaInfo.m_LowerBoundIsOpen) {
        if (value <= m_AttributeMetaInfo.m_LowerBound) {
          return false;
        }
      } else {
        if (value < m_AttributeMetaInfo.m_LowerBound) {
          return false;
        }
      }
      if (m_AttributeMetaInfo.m_UpperBoundIsOpen) {
        if (value >= m_AttributeMetaInfo.m_UpperBound) {
          return false;
        }
      } else {
        if (value > m_AttributeMetaInfo.m_UpperBound) {
          return false;
        }
      }
    }
    return true;
  }

  /**
   * Returns the revision string.
   * 
   * @return the revision
   */
  @Override
  public String getRevision() {
    return RevisionUtils.extract("$Revision$");
  }

  /**
   * Simple main method for testing this class.
   * 
   * @param ops the commandline options
   */
  // @ requires ops != null;
  // @ requires \nonnullelements(ops);
  public static void main(String[] ops) {

    try {

      new Attribute("length");
      Attribute weight = new Attribute("weight");

      // Create date attribute "date"
      Attribute date = new Attribute("date", "yyyy-MM-dd HH:mm:ss");

      System.out.println(date);
      double dd = date.parseDate("2001-04-04 14:13:55");
      System.out.println("Test date = " + dd);
      System.out.println(date.formatDate(dd));

      dd = new Date().getTime();
      System.out.println("Date now = " + dd);
      System.out.println(date.formatDate(dd));

      // Create vector to hold nominal values "first", "second", "third"
      List<String> my_nominal_values = new ArrayList<String>(3);
      my_nominal_values.add("first");
      my_nominal_values.add("second");
      my_nominal_values.add("third");

      // Create nominal attribute "position"
      Attribute position = new Attribute("position", my_nominal_values);

      // Print the name of "position"
      System.out.println("Name of \"position\": " + position.name());

      // Print the values of "position"
      Enumeration<Object> attValues = position.enumerateValues();
      while (attValues.hasMoreElements()) {
        String string = (String) attValues.nextElement();
        System.out.println("Value of \"position\": " + string);
      }

      // Shallow copy attribute "position"
      Attribute copy = (Attribute) position.copy();

      // Test if attributes are the same
      System.out.println("Copy is the same as original: "
        + copy.equals(position));

      // Print index of attribute "weight" (should be unset: -1)
      System.out.println("Index of attribute \"weight\" (should be -1): "
        + weight.index());

      // Print index of value "first" of attribute "position"
      System.out
        .println("Index of value \"first\" of \"position\" (should be 0): "
          + position.indexOfValue("first"));

      // Tests type of attribute "position"
      System.out.println("\"position\" is numeric: " + position.isNumeric());
      System.out.println("\"position\" is nominal: " + position.isNominal());
      System.out.println("\"position\" is string: " + position.isString());

      // Prints name of attribute "position"
      System.out.println("Name of \"position\": " + position.name());

      // Prints number of values of attribute "position"
      System.out.println("Number of values for \"position\": "
        + position.numValues());

      // Prints the values (againg)
      for (int i = 0; i < position.numValues(); i++) {
        System.out.println("Value " + i + ": " + position.value(i));
      }

      // Prints the attribute "position" in ARFF format
      System.out.println(position);

      // Checks type of attribute "position" using constants
      switch (position.type()) {
      case Attribute.NUMERIC:
        System.out.println("\"position\" is numeric");
        break;
      case Attribute.NOMINAL:
        System.out.println("\"position\" is nominal");
        break;
      case Attribute.STRING:
        System.out.println("\"position\" is string");
        break;
      case Attribute.DATE:
        System.out.println("\"position\" is date");
        break;
      case Attribute.RELATIONAL:
        System.out.println("\"position\" is relation-valued");
        break;
      default:
        System.out.println("\"position\" has unknown type");
      }

      ArrayList<Attribute> atts = new ArrayList<Attribute>(1);
      atts.add(position);
      Instances relation = new Instances("Test", atts, 0);
      Attribute relationValuedAtt = new Attribute("test", relation);
      System.out.println(relationValuedAtt);
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}