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diff --git a/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/api/IQueryGroup.java b/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/api/IQueryGroup.java
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+++ b/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/api/IQueryGroup.java
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+/*******************************************************************************
+ * Copyright (c) 2010-2012, Mark Czotter, Istvan Rath and Daniel Varro
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-v20.html.
+ * 
+ * SPDX-License-Identifier: EPL-2.0
+ *******************************************************************************/
+package tools.refinery.viatra.runtime.api;
+
+import java.util.Set;
+
+/**
+ * Generic interface for group of query specifications.
+ * 
+ * <p>It handles more than one patterns as a group, and provides functionality to initialize the matchers together (which
+ * has performance benefits).
+ * 
+ * @author Mark Czotter
+ * 
+ */
+public interface IQueryGroup {
+
+    /**
+     * Initializes matchers for the group of patterns within an {@link ViatraQueryEngine}. If some of the pattern matchers are already
+     * constructed in the engine, no task is performed for them.
+     * 
+     * <p>
+     * This preparation step has the advantage that it prepares pattern matchers for an arbitrary number of patterns in a
+     * single-pass traversal of the model. 
+     * This is typically more efficient than traversing the model each time an individual pattern matcher is initialized on demand. 
+     * The performance benefit only manifests itself if the engine is not in wildcard mode.
+     * 
+     * @param engine
+     *            the existing VIATRA Query engine in which the matchers will be created.
+     * @throws ViatraQueryRuntimeException
+     *             if there was an error in preparing the engine
+     */
+    public void prepare(ViatraQueryEngine engine);
+
+    /**
+     * Returns the currently assigned {@link IQuerySpecification}s.
+     */
+    public Set<IQuerySpecification<?>> getSpecifications();
+
+}