/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.mahout.cf.taste.impl.recommender;
import org.apache.mahout.cf.taste.common.Refreshable;
import org.apache.mahout.cf.taste.common.TasteException;
import org.apache.mahout.cf.taste.impl.common.FastIDSet;
/**
* <p>
* Returns the "similarity" between two clusters of users, according to some definition of similarity.
* Subclassses define different notions of similarity.
* </p>
*
* @see TreeClusteringRecommender
*/
public interface ClusterSimilarity extends Refreshable {
/**
* @param cluster1
* first cluster of user IDs
* @param cluster2
* second cluster of user IDs
* @return "distance" between clusters; a bigger value means less similarity
* @throws TasteException
* if an error occurs while computing similarity, such as errors accessing an underlying
* {@link org.apache.mahout.cf.taste.model.DataModel}
* @throws IllegalArgumentException
* if either argument is null or empty
*/
double getSimilarity(FastIDSet cluster1, FastIDSet cluster2) throws TasteException;
}