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The S-Space Package is a Natural Language Processing library for distributional semantics representations. Distributional semantics representations model the meaning of words, phrases, and sentences as high dimensional vectors or probability distributions. The library includes common algorithms such as Latent Semantic Analysis, Random Indexing, and Latent Dirichlet Allocation. The S-Space package also includes software libraries for matrices, vectors, graphs, and numerous clustering algorithms.

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/*
 * Copyright 2011 David Jurgens
 *
 * This file is part of the S-Space package and is covered under the terms and
 * conditions therein.
 *
 * The S-Space package is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation and distributed hereunder to you.
 *
 * THIS SOFTWARE IS PROVIDED "AS IS" AND NO REPRESENTATIONS OR WARRANTIES,
 * EXPRESS OR IMPLIED ARE MADE.  BY WAY OF EXAMPLE, BUT NOT LIMITATION, WE MAKE
 * NO REPRESENTATIONS OR WARRANTIES OF MERCHANT- ABILITY OR FITNESS FOR ANY
 * PARTICULAR PURPOSE OR THAT THE USE OF THE LICENSED SOFTWARE OR DOCUMENTATION
 * WILL NOT INFRINGE ANY THIRD PARTY PATENTS, COPYRIGHTS, TRADEMARKS OR OTHER
 * RIGHTS.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see .
 */

package edu.ucla.sspace.graph.isomorphism;

import java.util.Map;

import edu.ucla.sspace.graph.Edge;
import edu.ucla.sspace.graph.Graph;

import edu.ucla.sspace.util.Pair;

/**
 * An interface for representing the partial or complete state of an a attempted
 * isomorphic mapping between two graphs.  This interface exposes as set of
 * common operations used by {@link AbstractIsomorphismTester} to detect
 * isomorphism in a general manner while leaving the algorithm specifics
 * isolated to a {@link State} implementation.
 */
public interface State  {

    /**
     * The node marker to be used when indicating that that no node is being
     * matched. 
     */
    public static final int NULL_NODE = -1;

    /**
     * Returns the first graph being matched 
     */
    Graph getGraph1();

    /**
     * Returns the first graph being matched 
     */
    Graph getGraph2();

    /**
     * Returns the next candidate for isomorphic matching given these prior two
     * vertices that were matched.  If {@code prevN1} and {@code prevN1} are
     * {@code NULL_NODE}, this should return the initial candidate.
     */
    Pair nextPair(int prevN1, int prevN2);

    /**
     * Adds the two vertices to this {@code State}'s vertex mapping.
     */ 
    void addPair(int n1, int n2);

    /**
     * Returns {@code true} if mapping {@code node1} to {@code node2} would
     * preseve the isomorphism between the graphs to the extend that their
     * vertices have been mapped thusfar.
     */
    boolean isFeasiblePair(int node1, int node2);

    /**
     * Returns {@code true} if all the vertices have been mapped.  Equivalently,
     * returns {@code true} if the graphs are isomorphic.
     */
    boolean isGoal();

    /**
     * Returns {@code true} if the current state of mapping cannot proceed
     * because some invalid mapping has occurred and no further pairs would
     * result in an isomorphic match.
     */
    boolean isDead();

    /**
     * Returns the current mapping between vertices.
     */
    Map getVertexMapping();

    /**
     * Makes a shallow copy of the content of this state.
     */
    State copy();

    /**
     * Undoes the mapping added in the prior call to {@code addPair}.
     */
    void backTrack();
}