org.lenskit.api.RatingPredictor Maven / Gradle / Ivy
/*
* LensKit, an open source recommender systems toolkit.
* Copyright 2010-2014 LensKit Contributors. See CONTRIBUTORS.md.
* Work on LensKit has been funded by the National Science Foundation under
* grants IIS 05-34939, 08-08692, 08-12148, and 10-17697.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of the
* License, or (at your option) any later version.
*
* This program 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
* this program; if not, write to the Free Software Foundation, Inc., 51
* Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
package org.lenskit.api;
import javax.annotation.Nonnull;
import java.util.Collection;
import java.util.Map;
/**
* Predict user ratings. A rating predictor is like an {@link ItemScorer}, but its output is scaled or otherwise
* transformed for rating prediction. An item score can be anything that meets the requirement 'higher is better';
* a rating prediction can be interpreted as an estimate of the user's expected rating, within the system's stated
* range of valid ratings. Depending on the predictor used, rating predictions may also be quantized.
*
* @compat Public
*/
public interface RatingPredictor {
/**
* Predict a user's rating for a single item.
*
* @param user The user ID for whom to generate a prediction.
* @param item The item ID whose rating is to be predicted.
* @return The predicted preference, or {@link Double#NaN} if no preference can be
* predicted.
*/
Result predict(long user, long item);
/**
* Predict the user's preference for a collection of items.
*
* @param user The user ID for whom to generate predicts.
* @param items The items to predict for.
* @return A mapping from item IDs to predicted preference. This mapping may
* not contain all requested items.
*/
@Nonnull
Map predict(long user, @Nonnull Collection items);
/**
* Predict the user's preference for a collection of items, potentially with additional details.
*
* @param user The user ID for whom to generate predicts.
* @param items The items to predict for.
* @return A mapping from item IDs to predicted preference. This mapping may
* not contain all requested items.
*/
@Nonnull
ResultMap predictWithDetails(long user, @Nonnull Collection items);
}