/*
* Copyright 2010 Research Studios Austria Forschungsgesellschaft mBH
*
* This file is part of easyrec.
*
* easyrec is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* easyrec is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with easyrec. If not, see <http://www.gnu.org/licenses/>.
*/
package org.easyrec.plugin.slopeone;
import org.easyrec.model.core.RatingVO;
import org.easyrec.plugin.slopeone.model.DeviationCalculationResult;
import java.util.Date;
import java.util.List;
/**
* Interface defining methods needed for calculating the (average) deviations used in Slope One. <p/>
* <p><b>Company: </b> SAT, Research Studios Austria</p> <p/> <p><b>Copyright: </b> (c) 2007</p> <p/>
* <p><b>last modified:</b><br/> $Author: dmann $<br/> $Date: 2011-12-20 15:22:22 +0100 (Di, 20 Dez 2011) $<br/> $Revision: 18685 $</p>
*
* @author Patrick Marschik
*/
public interface DeviationCalculationStrategy {
// -------------------------- OTHER METHODS --------------------------
/**
* Calculates all possible deviations for a user.
* <p/>
* Deviations are calculated by using ratings x ratings, if both ratings are before {@code oldRatingsBeforeThisDate}
* the deviation is't calculated since this would duplicate eralier calculations.
*
* @param userId User the deviations are calculated for.
* @param ratings All ratings of that user.
* @param oldRatingsBeforeThisDate If ratings from the {@code ratings} List are both older than this date the
* deviation will not be calculated.
* @return Deviations calculated for this user.
*/
DeviationCalculationResult calculate(int userId, List<RatingVO<Integer, Integer>> ratings,
Date oldRatingsBeforeThisDate);
}