ClusteringCoefficientBase.java

/*
 * Copyright © 2014 - 2021 Leipzig University (Database Research Group)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.gradoop.flink.algorithms.gelly.clusteringcoefficient;

import org.apache.flink.graph.Graph;
import org.apache.flink.types.NullValue;
import org.gradoop.common.model.api.entities.Edge;
import org.gradoop.common.model.api.entities.GraphHead;
import org.gradoop.common.model.api.entities.Vertex;
import org.gradoop.common.model.impl.id.GradoopId;
import org.gradoop.flink.algorithms.gelly.GradoopGellyAlgorithm;
import org.gradoop.flink.algorithms.gelly.functions.EdgeToGellyEdgeWithNullValue;
import org.gradoop.flink.algorithms.gelly.functions.VertexToGellyVertexWithNullValue;
import org.gradoop.flink.model.api.epgm.BaseGraph;
import org.gradoop.flink.model.api.epgm.BaseGraphCollection;

/**
 * Base class for Gradoop EPGM model wrapper for Flink Gellys implementation of the clustering coefficient
 * algorithm. Implementations compute the local and global clustering coefficient of a graph, where:
 * <pre>
 *   local - connectedness of a single vertex regarding the connections of its neighborhood, with
 *           value between 0.0 (no edges between neighbors) and 1.0 (neighbors fully connected)
 *   global - connectedness of the graph as ratio from closed triplets (triangles) to all triplets
 *            with value between 0.0 (no closed triplets) and 1.0 (all triplets closed)
 * </pre>
 *
 * @param <G>  Gradoop graph head type.
 * @param <V>  Gradoop vertex type.
 * @param <E>  Gradoop edge type.
 * @param <LG> Gradoop type of the graph.
 * @param <GC> Gradoop type of the graph collection.
 */
public abstract class ClusteringCoefficientBase<
  G extends GraphHead,
  V extends Vertex,
  E extends Edge,
  LG extends BaseGraph<G, V, E, LG, GC>,
  GC extends BaseGraphCollection<G, V, E, LG, GC>>
  extends GradoopGellyAlgorithm<G, V, E, LG, GC, NullValue, NullValue> {

  /**
   * Property key to access the local clustering coefficient value stored in the vertices
   */
  public static final String PROPERTY_KEY_LOCAL = "clustering_coefficient_local";

  /**
   * Property key to access the global clustering coefficient value stored the graph head
   */
  public static final String PROPERTY_KEY_GLOBAL = "clustering_coefficient_global";

  /**
   * Creates an instance of the ClusteringCoefficientBase wrapper class.
   * Calls constructor of super class {@link GradoopGellyAlgorithm}
   */
  public ClusteringCoefficientBase() {
    super(new VertexToGellyVertexWithNullValue<>(),
      new EdgeToGellyEdgeWithNullValue<>());
  }

  @Override
  public LG executeInGelly(Graph<GradoopId, NullValue, NullValue> gellyGraph) throws Exception {
    return executeInternal(gellyGraph);
  }

  /**
   * Executes the computation of the clustering coefficient.
   *
   * @param gellyGraph Gelly graph with initialized vertices
   * @return {@link BaseGraph} with local values written to the vertices or global value
   * written to the graph head
   * @throws Exception Thrown if the gelly algorithm fails
   */
  protected abstract LG executeInternal(Graph<GradoopId, NullValue, NullValue> gellyGraph) throws Exception;
}