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diff --git a/plugins/org.eclipse.sirius.common/src/org/eclipse/sirius/common/tools/internal/interpreter/PolymorphicService.java b/plugins/org.eclipse.sirius.common/src/org/eclipse/sirius/common/tools/internal/interpreter/PolymorphicService.java
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index 0000000000..4c6c5c70a5
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+++ b/plugins/org.eclipse.sirius.common/src/org/eclipse/sirius/common/tools/internal/interpreter/PolymorphicService.java
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+/*******************************************************************************
+ * Copyright (c) 2013 THALES GLOBAL SERVICES.
+ * 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:
+ *    Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.sirius.common.tools.internal.interpreter;
+
+import java.util.List;
+import java.util.Set;
+
+import com.google.common.base.Preconditions;
+import com.google.common.base.Predicate;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
+
+import org.eclipse.sirius.common.tools.api.interpreter.EvaluationException;
+
+/**
+ * A service which corresponds to more than one Java method. Which of the
+ * methods will actually be invoked will depend on the target object.
+ * 
+ * @author pcdavid
+ */
+class PolymorphicService implements IService {
+    private final String name;
+
+    private final Set<MonomorphicService> implementers = Sets.newLinkedHashSet();
+
+    public PolymorphicService(String name) {
+        this.name = Preconditions.checkNotNull(name);
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void addImplementer(MonomorphicService svc) {
+        Preconditions.checkNotNull(svc);
+        Preconditions.checkArgument(name.equals(svc.getName()));
+        implementers.add(svc);
+    }
+
+    public boolean appliesTo(Object target) {
+        return Iterables.any(implementers, getCompatibilityChecker(target));
+    }
+
+    public Object call(Object target) throws EvaluationException {
+        List<MonomorphicService> candidates = Lists.newArrayList(Iterables.filter(implementers, getCompatibilityChecker(target)));
+        if (!candidates.isEmpty()) {
+            return candidates.get(0).call(target);
+        } else {
+            throw new EvaluationException("No compatible implementation of service " + getName() + " found for " + target);
+        }
+    }
+
+    private Predicate<MonomorphicService> getCompatibilityChecker(final Object target) {
+        Predicate<MonomorphicService> isCompatible = new Predicate<MonomorphicService>() {
+            public boolean apply(MonomorphicService svc) {
+                return svc.appliesTo(target);
+            }
+        };
+        return isCompatible;
+    }
+
+    @Override
+    public String toString() {
+        return "Polymorphic service " + getName() + " (" + implementers.size() + " implementations).";
+    }
+}