import java.util.*;
import java.io.*;

/** A class the represents a bare-bones OWL ontology. Essentially, the architecture is
 *  frame/slot approach similar to the underlying model of Protege. In this case, each
 *  "frame" is an OwlClass object and each "slot" is an OwlProperty object. 
 *  Note, to ensure compatibility with older versions of Java, the various data structures
 *  are not parameterized.*/
public class OwlOnt{
  
  /** A data structure that contain objects for each class in the ontology,
   allowing efficient lookup by URI of the class. */
  protected Hashtable classes;
  
  public OwlOnt() {
    
    classes = new Hashtable();
  }
  
  /** Returns an array of all classes defined in the ontology. */
  public OwlClass[] getClasses() {
    
    OwlClass[] classArray;
    OwlClass nextClass;
    int i = 0;
    
    classArray = new OwlClass[classes.size()];
    Enumeration classEnum = classes.elements();
    while (classEnum.hasMoreElements()) {
      nextClass = (OwlClass)classEnum.nextElement();
      classArray[i] = nextClass;
      i = i +1;
    }      
    return classArray;
  }
  
  /** Given the URI of a class, returns an object that represents it.
   If there is no class with that ID, returns null. */
  public OwlClass getClass(String classId) {
    
    Object lookup;
    
    lookup = classes.get(classId);
    if (lookup == null)
      return null;
    else
      return (OwlClass)lookup;
  }
  
  
  /** Returns true if the child class is a subclass of the parent,
   either directly or through the transitivity of subClassOf. */
  public boolean isSubClassOf(String childId, String parentId) {
    
    // *****  YOU NEED TO WRITE THIS METHOD!!!  *****
    
    return false;     // temporary return value so that program compiles
  }
  
  /** Reads an ontology from the given reader, parses it, and
   creates new OwlClass objects representing its contents.*/
  public void parseOntology(InputStream in) {
    
    // *****  YOU NEED TO WRITE THIS METHOD!!!  *****
  }
  
  /** Adds a class to the ontology. Inserts it into the classes
   hashtable with its id as a key. */
  protected void addClass(OwlClass newClass) {
    
    String classId;
    
    classId = newClass.getId();
    classes.put(classId,newClass);
    newClass.setOntology(this);
  }
}