Added newly specified "FoldIn" interface

src/org/mymedialite/itemrec/IFoldInItemRecommender.java

@@ -0,0 +1,47 @@
+//Copyright (C) 2012 Zeno Gantner
+//
+//This file is part of MyMediaLite.
+//
+//MyMediaLite 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.
+//
+//MyMediaLite 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 MyMediaLite. If not, see <http://www.gnu.org/licenses/>.
+//
+
+package org.mymedialite.itemrec;
+
+import java.util.List;
+import org.mymedialite.IRecommender;
+import org.mymedialite.data.WeightedItem;
+
+/**
+ * Rating predictor that allows folding in new users.
+ * 
+ * The process of folding in is computing a predictive model for a new user based on their ratings
+ * and the existing recommender, without modifying the parameters of the existing recommender.
+ * 
+ * Literature:
+ *    Badrul Sarwar and George Karypis, Joseph Konstan, John Riedl:
+ *    Incremental singular value decomposition algorithms for highly scalable recommender systems.
+ *    Fifth International Conference on Computer and Information Science, 2002.
+ *    http://grouplens.org/papers/pdf/sarwar_SVD.pdf
+ */
+public interface IFoldInItemRecommender extends IRecommender {
+
+  /**
+   * Score a list of items given a list of items that represent a new user.
+   * @return a list of WeightedItems, representing item IDs and predicted scores
+   * @param accessed_items the ratings (item IDs and rating values) representing the new user
+   * @param candidate_items the items to be rated
+   */
+  List<WeightedItem> scoreItems(List<Integer> accessed_items, List<Integer> candidate_items);
+
+}