import java.util.Iterator;

/**
 * The InspectableTree interface specifies an ordered tree the elements of which
 * are associated with positions.  The tree cannot be changed.
 *
 * @version     1.4    March 4, 2001
 * @author      Franck van Breugel
 * @see Position
 */
public interface InspectableTree extends InspectablePositionalContainer 
{
    /**
     * Returns the root of this tree.
     * @return The root of this tree.
     */
    public Position root();

    /**
     * Returns the parent of the specified position.
     * Throws an InvalidPositionException if the specified position is the root of
     * the tree.
     * @param position The position the parent of which is to be returned.
     * @return The parent of the specified position.
     * @exception InvalidPositionException if the specified position is the root of
     * the tree.
     */
    public Position parent(Position position) throws InvalidPositionException;

    /**
     * Returns the children of the specified position.
     * @param position The position the children of which are to be returned.
     * @return The children of the specified position.
     */
    public Iterator children(Position position);

    /**
     * Tests if the specified position is internal.
     * @param position The position to be tested to be internal.
     * @return true id the specified position is internal, false otherwise.
     */
    public boolean isInternal(Position position);

    /**
     * Tests if the specified position is external.
     * @param position The position to be tested to be external.
     * @return true id the specified position is external, false otherwise.
     */
    public boolean isExternal(Position position);

    /**
     * Tests if the specified position is the root of this tree.
     * @param position The position to be tested to be the root of this tree.
     * @return true id the specified position is the root, false otherwise.
     */
    public boolean isRoot(Position position);
}