Import Upstream version 0.4.0~beta1

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diff --git a/src/de/lmu/ifi/dbs/elki/math/linearalgebra/pca/weightfunctions/WeightFunction.java b/src/de/lmu/ifi/dbs/elki/math/linearalgebra/pca/weightfunctions/WeightFunction.java
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+package de.lmu.ifi.dbs.elki.math.linearalgebra.pca.weightfunctions;
+/*
+This file is part of ELKI:
+Environment for Developing KDD-Applications Supported by Index-Structures
+
+Copyright (C) 2011
+Ludwig-Maximilians-Universität München
+Lehr- und Forschungseinheit für Datenbanksysteme
+ELKI Development Team
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License as published by
+the Free Software Foundation, either version 3 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 Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+import de.lmu.ifi.dbs.elki.utilities.InspectionUtilFrequentlyScanned;
+
+/**
+ * WeightFunction interface that allows the use of various distance-based weight
+ * functions. In addition to the distance parameter, the maximum distance and
+ * standard deviation are also given, to allow distance functions to be
+ * normalized according to the maximum or standard deviation.
+ * 
+ * @author Erich Schubert
+ */
+public interface WeightFunction extends InspectionUtilFrequentlyScanned {
+  /**
+   * Evaluate weight function with given parameters.
+   * 
+   * Note that usually implementations will ignore either max or stddev.
+   * 
+   * @param distance distance of the query point
+   * @param max maximum distance of all included points
+   * @param stddev standard deviation (i.e. quadratic mean / RMS) of the
+   *        included points
+   * @return weight for the query point
+   */
+  double getWeight(double distance, double max, double stddev);
+}