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diff --git a/bundles/org.eclipse.equinox.p2.metadata/src/org/eclipse/equinox/internal/provisional/p2/metadata/query/ContextQuery.java b/bundles/org.eclipse.equinox.p2.metadata/src/org/eclipse/equinox/internal/provisional/p2/metadata/query/ContextQuery.java
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+++ b/bundles/org.eclipse.equinox.p2.metadata/src/org/eclipse/equinox/internal/provisional/p2/metadata/query/ContextQuery.java
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+/******************************************************************************* 
+* Copyright (c) 2009 EclipseSource and others. All rights reserved. This
+* program and the accompanying materials are made available under the terms of
+* the Eclipse Public License v1.0 which accompanies this distribution, and is
+* available at http://www.eclipse.org/legal/epl-v10.html
+*
+* Contributors:
+*   EclipseSource - initial API and implementation
+******************************************************************************/
+package org.eclipse.equinox.internal.provisional.p2.metadata.query;
+
+
+import java.util.Iterator;
+
+/**
+ * ContextQuery is the abstract superclass for Queries that require the entire
+ * input to evaluate the results.  Queries must consider the group of elements before
+ * processing the results. <P>
+ * 
+ * ContextQueries must also be transitive. That is, if run on a subset of the 
+ * input, the order in which they are executed must not matter. If there is the 
+ * need for a non-transitive query, please see:
+ * https://bugs.eclipse.org/bugs/show_bug.cgi?id=261403
+ * <p>
+ * Users of this query must call {@link #perform(Iterator, Collector)} to compute 
+ * the results. <P>
+ * This class may be subclassed by clients. Subclasses should specify the type
+ * of object they support querying on. Subclasses are also encouraged to clearly
+ * specify their match algorithm, and expose the parameters involved in the match
+ * computation, to allow {@link IQueryable} implementations to optimize their
+ * execution of the query. <P>
+ * 
+ */
+public abstract class ContextQuery implements Query {
+
+	/**
+	 * Evaluates the query for a specific input.  
+	 * 
+	 * @param iterator The elements for which to evaluate the query on
+	 * @param result A collector to collect the results.  For each element accepted 
+	 * by the query,{@link Collector#accept(Object)} must be called.
+	 * @return The results of the query.  The collector returned must be
+	 * the collector passed in.
+	 */
+	public abstract Collector perform(Iterator iterator, Collector result);
+
+	/**
+	 * Gets the ID for this Query. 
+	 */
+	public String getId() {
+		return QueryHelpers.getId(this);
+	}
+
+	/**
+	 * Gets a particular property of the query.
+	 * @param property The property to retrieve 
+	 */
+	public Object getProperty(String property) {
+		return QueryHelpers.getProperty(this, property);
+	}
+}