[496014] Add extension point to contribute IInterpretedExpressionQueryProviders

Bug: 496014
Change-Id: I3d0177448e014716c2997303f084afb7f0e27afd
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>

10 files changed, 365 insertions, 127 deletions

diff --git a/plugins/org.eclipse.sirius.doc/doc/Release_Notes.html b/plugins/org.eclipse.sirius.doc/doc/Release_Notes.html
index a88b4393e4..288415824b 100644
--- a/plugins/org.eclipse.sirius.doc/doc/Release_Notes.html
+++ b/plugins/org.eclipse.sirius.doc/doc/Release_Notes.html
@@ -160,6 +160,12 @@
 			<code>org.eclipse.sirius</code>
 		</h4>
 		<ul>
+			<li><span class="label label-success">Added</span> A new extension point named 
+				<code>org.eclipse.sirius.interpretedExpressionQueryProvider</code> (with the associated new interface 
+				<code>org.eclipse.sirius.business.api.dialect.description.IInterpretedExpressionQueryProvider</code>) allows external contribution of 
+				<code>IInterpretedExpressionQuery</code> specific to some particular expression occurrences in the VSM. This is used in particular for VSM extensions which do not fit well into the hard-coded assumptions about 
+				<code>IInterpretedExpressionQuery</code>. In Sirius 4.1, this is used to add completion and validation support for expressions used in properties views descriptions.
+			</li>
 			<li><span class="label label-success">Added</span> 
 				<code>org.eclipse.sirius.business.api.migration.AirdResourceVersionMismatchException</code> exception has been added to cancel Sirius session opening due to an .aird version mismatch, i.e. when one the of the loaded Representation resources is coming from a newer Sirius release.
 			</li>
diff --git a/plugins/org.eclipse.sirius.doc/doc/Release_Notes.textile b/plugins/org.eclipse.sirius.doc/doc/Release_Notes.textile
index df7e127be0..1229cf944a 100644
--- a/plugins/org.eclipse.sirius.doc/doc/Release_Notes.textile
+++ b/plugins/org.eclipse.sirius.doc/doc/Release_Notes.textile
@@ -32,6 +32,7 @@ h4. Changes in @org.eclipse.sirius.common@
 
 h4. Changes in @org.eclipse.sirius@
 
+* <span class="label label-success">Added</span> A new extension point named @org.eclipse.sirius.interpretedExpressionQueryProvider@ (with the associated new interface @org.eclipse.sirius.business.api.dialect.description.IInterpretedExpressionQueryProvider@) allows external contribution of @IInterpretedExpressionQuery@ specific to some particular expression occurrences in the VSM. This is used in particular for VSM extensions which do not fit well into the hard-coded assumptions about @IInterpretedExpressionQuery@. In Sirius 4.1, this is used to add completion and validation support for expressions used in properties views descriptions.
 * <span class="label label-success">Added</span> @org.eclipse.sirius.business.api.migration.AirdResourceVersionMismatchException@ exception has been added to cancel Sirius session opening due to an .aird version mismatch, i.e. when one the of the loaded Representation resources is coming from a newer Sirius release.
 * <span class="label label-success">Added</span> @org.eclipse.sirius.viewpoint.DView.getOwnedRepresentationDescriptors()@ has been added as the first step to save the DRepresentation in its own resource. In this step, the DRepresentationDescriptor life cycle is the same as the associated DRepresentation.
 ** @org.eclipse.sirius.business.api.dialect.command.RenameRepresentationCommand@
diff --git a/plugins/org.eclipse.sirius/plugin.properties b/plugins/org.eclipse.sirius/plugin.properties
index ba8bb04fa4..da6defd960 100644
--- a/plugins/org.eclipse.sirius/plugin.properties
+++ b/plugins/org.eclipse.sirius/plugin.properties
@@ -57,6 +57,7 @@ extension-point.deleteHook.name = org.eclipse.sirius.deleteHook
 extension-point.dialect.name = org.eclipse.sirius.dialect
 extension-point.externalJavaAction = External Java Actions
 extension-point.featureExtensions.name = org.eclipse.sirius.featureExtensions
+extension-point.interpretedExpressionQueryProvider.name = org.eclipse.sirius.interpretedExpressionQueryProvider
 extension-point.migration.name = org.eclipse.sirius.migration
 extension-point.mmdescriptor.name = org.eclipse.sirius.mmdescriptor
 extension-point.refreshExtensionProvider.name = viewpoint.semantic.refresh.refreshExtensionProvider
@@ -173,6 +174,7 @@ InitializeModelingProjectJob_invalidModelingProjectErrorMsg = One modeling proje
 InitializeModelingProjectJob_label = Initializing Modeling Projects
 InitializeModelingProjectJob_labelEmptyProject = Initializing Empty Modeling Projects
 InterpretedExpressionVariableTask_label = set or unset an acceleo variable task
+InterpretedExpressionQueryProviderRegistry_instanciationError = An error occurred while trying to instanciate {0} as an IInterpretedExpressionQueryProvider.
 InterpreterRegistry_sessionNotFoundErrorMsg = Could not find a session for model element : {0}
 InterpreterRegistry_nullModelElementErrorMsg = Model element is null
 InterpreterRegistry_ImpossibleToFindInterpreterErrorMsg = Impossible to find an interpreter
diff --git a/plugins/org.eclipse.sirius/plugin.xml b/plugins/org.eclipse.sirius/plugin.xml
index b400593791..5dbff596f0 100644
--- a/plugins/org.eclipse.sirius/plugin.xml
+++ b/plugins/org.eclipse.sirius/plugin.xml
@@ -28,6 +28,7 @@
    <extension-point id="migrationParticipant" name="%extension-point.migration.name" schema="schema/migrationParticipant.exsd"/>
    <extension-point id="repairParticipant" name="%extension-point.repairParticipant.name" schema="schema/repairParticipant.exsd"/>
    <extension-point id="resourceStrategy" name="%extension-point.resourceStrategy.name" schema="schema/resourceStrategy.exsd"/>
+   <extension-point id="interpretedExpressionQueryProvider" name="%extension-point.interpretedExpressionQueryProvider.name" schema="schema/interpretedExpressionQueryProvider.exsd"/>
 
    <extension point="org.eclipse.emf.ecore.generated_package">
       <!-- @generated viewpoint -->
diff --git a/plugins/org.eclipse.sirius/schema/interpretedExpressionQueryProvider.exsd b/plugins/org.eclipse.sirius/schema/interpretedExpressionQueryProvider.exsd
new file mode 100644
index 0000000000..56a93a218e
--- /dev/null
+++ b/plugins/org.eclipse.sirius/schema/interpretedExpressionQueryProvider.exsd
@@ -0,0 +1,114 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<!-- Schema file written by PDE -->
+<schema targetNamespace="org.eclipse.sirius" xmlns="http://www.w3.org/2001/XMLSchema">
+<annotation>
+      <appInfo>
+         <meta.schema plugin="org.eclipse.sirius" id="interpretedExpressionQueryProvider" name="org.eclipse.sirius.interpretedExpressionQueryProvider"/>
+      </appInfo>
+      <documentation>
+         This extension points allows external contribution of &lt;code&gt;IInterpretedExpressionQuery&lt;/code&gt; specific to some particular expression occurrence in the VSM. This is used in particular for VSM extensions which do not fit well into the hard-coded assumptions about &lt;code&gt;IInterpretedExpressionQuery&lt;/code&gt;, which normally assumes interpreted expressions only occur inside the context of a dialect / representation description.
+      </documentation>
+   </annotation>
+
+   <element name="extension">
+      <annotation>
+         <appInfo>
+            <meta.element />
+         </appInfo>
+      </annotation>
+      <complexType>
+         <sequence>
+            <element ref="interpretedExpressionProvider" minOccurs="1" maxOccurs="unbounded"/>
+         </sequence>
+         <attribute name="point" type="string" use="required">
+            <annotation>
+               <documentation>
+                  
+               </documentation>
+            </annotation>
+         </attribute>
+         <attribute name="id" type="string">
+            <annotation>
+               <documentation>
+                  
+               </documentation>
+            </annotation>
+         </attribute>
+         <attribute name="name" type="string">
+            <annotation>
+               <documentation>
+                  
+               </documentation>
+               <appInfo>
+                  <meta.attribute translatable="true"/>
+               </appInfo>
+            </annotation>
+         </attribute>
+      </complexType>
+   </element>
+
+   <element name="interpretedExpressionProvider">
+      <complexType>
+         <attribute name="class" type="string" use="required">
+            <annotation>
+               <documentation>
+                  
+               </documentation>
+               <appInfo>
+                  <meta.attribute kind="java" basedOn=":org.eclipse.sirius.business.api.dialect.description.IInterpretedExpressionQueryProvider"/>
+               </appInfo>
+            </annotation>
+         </attribute>
+      </complexType>
+   </element>
+
+   <annotation>
+      <appInfo>
+         <meta.section type="since"/>
+      </appInfo>
+      <documentation>
+         Sirius 4.1.0.
+      </documentation>
+   </annotation>
+
+   <annotation>
+      <appInfo>
+         <meta.section type="examples"/>
+      </appInfo>
+      <documentation>
+         See &lt;code&gt;org.eclipse.sirius.ui.properties.internal.expressions.PropertiesInterpretedExpressionQuery&lt;/code&gt; which uses this mechanism to plug completion and validation support for expressions used in property views descriptions.
+      </documentation>
+   </annotation>
+
+   <annotation>
+      <appInfo>
+         <meta.section type="apiinfo"/>
+      </appInfo>
+      <documentation>
+         See &lt;code&gt;org.eclipse.sirius.business.api.dialect.description.IInterpretedExpressionQueryProvider&lt;/code&gt; and &lt;code&gt;org.eclipse.sirius.business.api.dialect.description.IInterpretedExpressionQuery&lt;/code&gt;.
+      </documentation>
+   </annotation>
+
+   <annotation>
+      <appInfo>
+         <meta.section type="implementation"/>
+      </appInfo>
+      <documentation>
+         None.
+      </documentation>
+   </annotation>
+
+   <annotation>
+      <appInfo>
+         <meta.section type="copyright"/>
+      </appInfo>
+      <documentation>
+         Copyright (c) 2016 Obeo.
+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
+      </documentation>
+   </annotation>
+
+</schema>
diff --git a/plugins/org.eclipse.sirius/src/org/eclipse/sirius/business/api/dialect/description/IInterpretedExpressionQueryProvider.java b/plugins/org.eclipse.sirius/src/org/eclipse/sirius/business/api/dialect/description/IInterpretedExpressionQueryProvider.java
new file mode 100644
index 0000000000..83f9495c63
--- /dev/null
+++ b/plugins/org.eclipse.sirius/src/org/eclipse/sirius/business/api/dialect/description/IInterpretedExpressionQueryProvider.java
@@ -0,0 +1,41 @@
+/*******************************************************************************
+ * Copyright (c) 2016 Obeo.
+ * 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.business.api.dialect.description;
+
+import org.eclipse.emf.ecore.EObject;
+import org.eclipse.emf.ecore.EStructuralFeature;
+import org.eclipse.sirius.ext.base.Option;
+
+/**
+ * Instances can provide <code>IInterpretedExpressionQuery</code> specific to
+ * some particular expression occurrence in the VSM.
+ * 
+ * @author pcdavid
+ */
+public interface IInterpretedExpressionQueryProvider {
+    /**
+     * Optionally provides an {@link IInterpretedExpressionQuery} for a specific
+     * interpreted expression occurrence.
+     * 
+     * @param context
+     *            the VSM element in which the expression to query occurs.
+     * @param expressionAttribute
+     *            the attribute of the context element which designates the
+     *            expression to consider (for example
+     *            {@link org.eclipse.sirius.viewpoint.description.DescriptionPackage.Literals#REPRESENTATION_DESCRIPTION__TITLE_EXPRESSION}
+     *            ) .
+     * @return an optional {@link IInterpretedExpressionQuery} that will query
+     *         representation descriptions to determine useful informations
+     *         (like the type to consider for Interpreted expressions).
+     * @return
+     */
+    Option<IInterpretedExpressionQuery> getExpressionQueryFor(EObject context, EStructuralFeature expressionAttribute);
+}
diff --git a/plugins/org.eclipse.sirius/src/org/eclipse/sirius/business/internal/dialect/DialectManagerImpl.java b/plugins/org.eclipse.sirius/src/org/eclipse/sirius/business/internal/dialect/DialectManagerImpl.java
index f559c90e48..4d0ceeeddc 100644
--- a/plugins/org.eclipse.sirius/src/org/eclipse/sirius/business/internal/dialect/DialectManagerImpl.java
+++ b/plugins/org.eclipse.sirius/src/org/eclipse/sirius/business/internal/dialect/DialectManagerImpl.java
@@ -21,7 +21,6 @@ import java.util.Map;
 import java.util.Set;
 
 import org.eclipse.core.runtime.IProgressMonitor;
-import org.eclipse.core.runtime.NullProgressMonitor;
 import org.eclipse.core.runtime.SubProgressMonitor;
 import org.eclipse.emf.common.notify.Notification;
 import org.eclipse.emf.ecore.EObject;
@@ -32,8 +31,10 @@ import org.eclipse.sirius.business.api.dialect.DialectManager;
 import org.eclipse.sirius.business.api.dialect.RepresentationNotification;
 import org.eclipse.sirius.business.api.dialect.description.DefaultInterpretedExpressionQuery;
 import org.eclipse.sirius.business.api.dialect.description.IInterpretedExpressionQuery;
+import org.eclipse.sirius.business.api.dialect.description.IInterpretedExpressionQueryProvider;
 import org.eclipse.sirius.business.api.dialect.identifier.RepresentationElementIdentifier;
 import org.eclipse.sirius.business.api.helper.task.AbstractCommandTask;
+import org.eclipse.sirius.business.api.query.EObjectQuery;
 import org.eclipse.sirius.business.api.session.Session;
 import org.eclipse.sirius.business.internal.movida.Movida;
 import org.eclipse.sirius.common.tools.api.util.EclipseUtil;
@@ -47,6 +48,7 @@ import org.eclipse.sirius.viewpoint.DRepresentationDescriptor;
 import org.eclipse.sirius.viewpoint.Messages;
 import org.eclipse.sirius.viewpoint.SiriusPlugin;
 import org.eclipse.sirius.viewpoint.ViewpointPackage;
+import org.eclipse.sirius.viewpoint.description.DescriptionPackage;
 import org.eclipse.sirius.viewpoint.description.RepresentationDescription;
 import org.eclipse.sirius.viewpoint.description.RepresentationExtensionDescription;
 import org.eclipse.sirius.viewpoint.description.Viewpoint;
@@ -81,10 +83,6 @@ public class DialectManagerImpl implements DialectManager {
         return manager;
     }
 
-    /**
-     * 
-     * {@inheritDoc}
-     */
     @Override
     public Collection<RepresentationDescription> getAvailableRepresentationDescriptions(final Collection<Viewpoint> vp, final EObject semantic) {
         final Collection<RepresentationDescription> descs = new ArrayList<RepresentationDescription>();
@@ -94,9 +92,6 @@ public class DialectManagerImpl implements DialectManager {
         return descs;
     }
 
-    /**
-     * {@inheritDoc}
-     */
     @Override
     public void refreshEffectiveRepresentationDescription(DRepresentation representation, IProgressMonitor monitor) {
         if (Movida.isEnabled()) {
@@ -106,17 +101,11 @@ public class DialectManagerImpl implements DialectManager {
         }
     }
 
-    /**
-     * {@inheritDoc}
-     */
     @Override
     public void refresh(final DRepresentation representation, final IProgressMonitor monitor) {
         refresh(representation, false, monitor);
     }
 
-    /**
-     * {@inheritDoc}
-     */
     @Override
     public void refresh(DRepresentation representation, boolean doFullRefresh, IProgressMonitor monitor) {
         try {
@@ -145,17 +134,6 @@ public class DialectManagerImpl implements DialectManager {
         }
     }
 
-    /**
-     * {@inheritDoc}
-     */
-    public DRepresentation createRepresentation(final String name, final EObject semantic, final RepresentationDescription description, final IProgressMonitor monitor) {
-        return createRepresentation(name, semantic, description, null, monitor);
-    }
-
-    /**
-     * 
-     * {@inheritDoc}
-     */
     @Override
     public DRepresentation createRepresentation(final String name, final EObject semantic, final RepresentationDescription description, final Session session, final IProgressMonitor monitor) {
         DRepresentation created = null;
@@ -190,13 +168,6 @@ public class DialectManagerImpl implements DialectManager {
         return created;
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.business.api.dialect.DialectServices#copyRepresentation(org.eclipse.sirius.viewpoint.DRepresentation,
-     *      java.lang.String, org.eclipse.sirius.business.api.session.Session,
-     *      org.eclipse.core.runtime.IProgressMonitor)
-     */
     @Override
     public DRepresentation copyRepresentation(final DRepresentation representation, final String name, final Session session, final IProgressMonitor monitor) {
         Dialect invokedDialect = null;
@@ -222,10 +193,6 @@ public class DialectManagerImpl implements DialectManager {
         return copy;
     }
 
-    /**
-     * 
-     * {@inheritDoc}
-     */
     @Override
     public boolean canRefresh(final DRepresentation representation) {
         for (final Dialect dialect : dialects.values()) {
@@ -236,10 +203,6 @@ public class DialectManagerImpl implements DialectManager {
         return false;
     }
 
-    /**
-     * 
-     * {@inheritDoc}
-     */
     @Override
     public boolean canCreate(final EObject semantic, final RepresentationDescription desc) {
         boolean canCreate = false;
@@ -256,31 +219,16 @@ public class DialectManagerImpl implements DialectManager {
         return canCreate;
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.business.api.dialect.DialectManager#disableDialect(org.eclipse.sirius.business.api.dialect.Dialect)
-     */
     @Override
     public void disableDialect(final Dialect dialect) {
         dialects.remove(dialect.getName());
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.business.api.dialect.DialectManager#enableDialect(org.eclipse.sirius.business.api.dialect.Dialect)
-     */
     @Override
     public void enableDialect(final Dialect dialect) {
         dialects.put(dialect.getName(), dialect);
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.business.api.dialect.DialectServices#notify(org.eclipse.sirius.business.api.dialect.RepresentationNotification)
-     */
     @Override
     public void notify(final RepresentationNotification representation) {
         for (final Dialect dialect : dialects.values()) {
@@ -396,11 +344,6 @@ public class DialectManagerImpl implements DialectManager {
 
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.business.api.dialect.DialectServices#getDescription(org.eclipse.sirius.viewpoint.DRepresentation)
-     */
     @Override
     public RepresentationDescription getDescription(final DRepresentation representation) {
         RepresentationDescription result = null;
@@ -411,16 +354,6 @@ public class DialectManagerImpl implements DialectManager {
         return result;
     }
 
-    /**
-     * {@inheritDoc}
-     */
-    public void initRepresentations(Viewpoint vp, EObject semantic) {
-        initRepresentations(vp, semantic, new NullProgressMonitor());
-    }
-
-    /**
-     * {@inheritDoc}
-     */
     @Override
     public void initRepresentations(final Viewpoint vp, final EObject semantic, IProgressMonitor monitor) {
         for (final Dialect dialect : dialects.values()) {
@@ -428,11 +361,6 @@ public class DialectManagerImpl implements DialectManager {
         }
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.business.api.dialect.DialectServices#canCreateIdentifier(org.eclipse.emf.ecore.EObject)
-     */
     @Override
     public boolean canCreateIdentifier(final EObject representationElement) {
         for (final Dialect dialect : dialects.values()) {
@@ -443,12 +371,6 @@ public class DialectManagerImpl implements DialectManager {
         return false;
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.business.api.dialect.DialectServices#createIdentifier(org.eclipse.emf.ecore.EObject,
-     *      java.util.Map)
-     */
     @Override
     public RepresentationElementIdentifier createIdentifier(final EObject representationElement, final Map<EObject, RepresentationElementIdentifier> elementToIdentifier) {
         for (final Dialect dialect : dialects.values()) {
@@ -460,12 +382,6 @@ public class DialectManagerImpl implements DialectManager {
         return null;
     }
 
-    /**
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.business.api.dialect.DialectServices#updateRepresentationsExtendedBy(Session,
-     *      Viewpoint, boolean)
-     */
     @Override
     public void updateRepresentationsExtendedBy(final Session session, final Viewpoint viewpoint, final boolean activated) {
         for (final Dialect dialect : dialects.values()) {
@@ -473,24 +389,28 @@ public class DialectManagerImpl implements DialectManager {
         }
     }
 
-    /**
-     * 
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.business.api.dialect.DialectServices#createInterpretedExpressionQuery(org.eclipse.emf.ecore.EObject,
-     *      org.eclipse.emf.ecore.EStructuralFeature)
-     */
     @Override
     public IInterpretedExpressionQuery createInterpretedExpressionQuery(EObject target, EStructuralFeature feature) {
         IInterpretedExpressionQuery returnedQuery = null;
-
-        // Step 1 : we search for a Dialect compatible with
-        // the given target
-        Dialect dialect = getDialectFromEObjectAccordingToRepresentationDescription(target);
-        if (dialect != null) {
-            // Step 2 : we delegate the query creation to the found
-            // DialectDescription
-            returnedQuery = dialect.getServices().createInterpretedExpressionQuery(target, feature);
+        // Ask registered providers first
+        for (IInterpretedExpressionQueryProvider provider : SiriusPlugin.getDefault().getInterpretedExpressionQueryProviders()) {
+            Option<IInterpretedExpressionQuery> answer = provider.getExpressionQueryFor(target, feature);
+            if (answer.some()) {
+                returnedQuery = answer.get();
+                break;
+            }
+        }
+        if (returnedQuery == null) {
+            // Step 1 : we search for a Dialect compatible with
+            // the given target
+            Dialect dialect = getDialectFromEObjectAccordingToRepresentationDescription(target);
+            if (dialect != null) {
+                // Step 2 : we delegate the query creation to the found
+                // DialectDescription
+                returnedQuery = dialect.getServices().createInterpretedExpressionQuery(target, feature);
+            } else if (new EObjectQuery(target).getFirstAncestorOfType(DescriptionPackage.Literals.EXTENSION).some()) {
+                // We are not inside a dialect, but inside an extension
+            }
         }
         if (returnedQuery != null) {
             return returnedQuery;
@@ -500,12 +420,6 @@ public class DialectManagerImpl implements DialectManager {
         return new DefaultInterpretedExpressionQuery(target, feature);
     }
 
-    /**
-     * 
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.business.api.dialect.DialectServices#handles(org.eclipse.sirius.viewpoint.description.RepresentationDescription)
-     */
     @Override
     public boolean handles(RepresentationDescription representationDescription) {
         for (Dialect dialect : dialects.values()) {
@@ -560,12 +474,6 @@ public class DialectManagerImpl implements DialectManager {
         return foundDialect;
     }
 
-    /**
-     * 
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.business.api.dialect.DialectServices#handles(org.eclipse.sirius.viewpoint.description.RepresentationExtensionDescription)
-     */
     @Override
     public boolean handles(RepresentationExtensionDescription representationExtensionDescription) {
         for (Dialect dialect : dialects.values()) {
@@ -576,12 +484,6 @@ public class DialectManagerImpl implements DialectManager {
         return false;
     }
 
-    /**
-     * 
-     * {@inheritDoc}
-     * 
-     * @see org.eclipse.sirius.business.api.dialect.DialectServices#invalidateMappingCache()
-     */
     @Override
     public void invalidateMappingCache() {
         for (Dialect dialect : dialects.values()) {
@@ -589,9 +491,6 @@ public class DialectManagerImpl implements DialectManager {
         }
     }
 
-    /**
-     * {@inheritDoc}
-     */
     @Override
     public Option<? extends AbstractCommandTask> createTask(CommandContext context, ModelAccessor extPackage, ModelOperation op, Session session, UICallBack uiCallback) {
         Option<? extends AbstractCommandTask> task = Options.newNone();
@@ -603,9 +502,6 @@ public class DialectManagerImpl implements DialectManager {
         return task;
     }
 
-    /**
-     * {@inheritDoc}
-     */
     @Override
     public boolean allowsEStructuralFeatureCustomization(EObject element) {
         boolean customizationAllowed = false;
diff --git a/plugins/org.eclipse.sirius/src/org/eclipse/sirius/business/internal/dialect/description/InterpretedExpressionQueryProviderRegistry.java b/plugins/org.eclipse.sirius/src/org/eclipse/sirius/business/internal/dialect/description/InterpretedExpressionQueryProviderRegistry.java
new file mode 100644
index 0000000000..46bb8e943a
--- /dev/null
+++ b/plugins/org.eclipse.sirius/src/org/eclipse/sirius/business/internal/dialect/description/InterpretedExpressionQueryProviderRegistry.java
@@ -0,0 +1,153 @@
+/*******************************************************************************
+ * Copyright (c) 2016 Obeo
+ * 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.business.internal.dialect.description;
+
+import java.text.MessageFormat;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Iterator;
+
+import org.eclipse.core.runtime.CoreException;
+import org.eclipse.core.runtime.IConfigurationElement;
+import org.eclipse.core.runtime.IExtension;
+import org.eclipse.core.runtime.IExtensionPoint;
+import org.eclipse.core.runtime.IExtensionRegistry;
+import org.eclipse.core.runtime.IRegistryEventListener;
+import org.eclipse.core.runtime.IStatus;
+import org.eclipse.core.runtime.Plugin;
+import org.eclipse.core.runtime.Status;
+import org.eclipse.sirius.business.api.dialect.description.IInterpretedExpressionQueryProvider;
+import org.eclipse.sirius.tools.internal.ui.ExternalJavaActionDescriptor;
+import org.eclipse.sirius.viewpoint.Messages;
+
+import com.google.common.base.Objects;
+import com.google.common.base.Preconditions;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
+
+/**
+ * Maintains the set of {@link IInterpretedExpressionQueryProvider} currently
+ * registered.
+ *
+ * @author pcdavid
+ */
+public class InterpretedExpressionQueryProviderRegistry {
+    /** Name of the extension point to parse. */
+    public static final String EXTENSION_POINT = "org.eclipse.sirius.interpretedExpressionQueryProvider"; //$NON-NLS-1$
+
+    /** The attributed used to designate the provider implementation class. */
+    public static final String CLASS_ATTRIBUTE = "class"; //$NON-NLS-1$
+
+    private final IExtensionRegistry registry;
+
+    private final Plugin context;
+
+    private final Collection<IInterpretedExpressionQueryProvider> entries;
+
+    private final IRegistryEventListener listener = new IRegistryEventListener() {
+
+        @Override
+        public void added(IExtension[] extensions) {
+            for (IExtension extension : extensions) {
+                for (IConfigurationElement elem : extension.getConfigurationElements()) {
+                    register(elem);
+                }
+            }
+        }
+
+        @Override
+        public void removed(IExtension[] extensions) {
+            for (IExtension extension : extensions) {
+                for (IConfigurationElement elem : extension.getConfigurationElements()) {
+                    unregister(elem);
+                }
+            }
+        }
+
+        @Override
+        public void added(IExtensionPoint[] extensionPoints) {
+            // no need to listen to this event
+        }
+
+        @Override
+        public void removed(IExtensionPoint[] extensionPoints) {
+            // no need to listen to this event
+        }
+    };
+
+    /**
+     * Constructor.
+     * 
+     * @param registry
+     *            the registry to look for registered providers.
+     * @param context
+     *            the plug-in in the context of which we're running; used for
+     *            logging.
+     */
+    public InterpretedExpressionQueryProviderRegistry(IExtensionRegistry registry, Plugin context) {
+        this.registry = Preconditions.checkNotNull(registry);
+        this.context = context;
+        this.entries = Sets.newConcurrentHashSet();
+    }
+
+    /**
+     * Register this listener and parse initial contributions.
+     */
+    public void init() {
+        registry.addListener(listener, InterpretedExpressionQueryProviderRegistry.EXTENSION_POINT);
+        IExtension[] initialExtensions = registry.getExtensionPoint(InterpretedExpressionQueryProviderRegistry.EXTENSION_POINT).getExtensions();
+        listener.added(initialExtensions);
+    }
+
+    /**
+     * Stop listening for further registry changes and forget about all
+     * currently known entries.
+     */
+    public void dispose() {
+        registry.removeListener(listener);
+        entries.clear();
+    }
+
+    /**
+     * Returns all the currently registered
+     * {@link IInterpretedExpressionQueryProvider}.
+     * 
+     * @return the currently registered
+     *         {@link IInterpretedExpressionQueryProvider}.
+     */
+    public Collection<IInterpretedExpressionQueryProvider> getEntries() {
+        return Collections.unmodifiableList(Lists.newArrayList(entries));
+    }
+
+    private void register(IConfigurationElement elem) {
+        Object executableExtension;
+        try {
+            executableExtension = elem.createExecutableExtension(CLASS_ATTRIBUTE);
+            if (executableExtension instanceof IInterpretedExpressionQueryProvider) {
+                entries.add((IInterpretedExpressionQueryProvider) executableExtension);
+            }
+        } catch (CoreException e) {
+            String message = MessageFormat.format(Messages.InterpretedExpressionQueryProviderRegistry_instanciationError, elem.getAttribute(CLASS_ATTRIBUTE));
+            context.getLog().log(new Status(IStatus.ERROR, context.getBundle().getSymbolicName(), message, e));
+        }
+    }
+
+    private void unregister(IConfigurationElement elem) {
+        String className = elem.getAttribute(ExternalJavaActionDescriptor.CLASS_ATTRIBUTE);
+        Iterator<IInterpretedExpressionQueryProvider> iter = entries.iterator();
+        while (iter.hasNext()) {
+            IInterpretedExpressionQueryProvider provider = iter.next();
+            if (Objects.equal(className, provider.getClass().getName())) {
+                iter.remove();
+            }
+        }
+    }
+}
diff --git a/plugins/org.eclipse.sirius/src/org/eclipse/sirius/viewpoint/Messages.java b/plugins/org.eclipse.sirius/src/org/eclipse/sirius/viewpoint/Messages.java
index 1308d23c60..35f5322d2a 100644
--- a/plugins/org.eclipse.sirius/src/org/eclipse/sirius/viewpoint/Messages.java
+++ b/plugins/org.eclipse.sirius/src/org/eclipse/sirius/viewpoint/Messages.java
@@ -331,6 +331,9 @@ public final class Messages {
 
     @TranslatableMessage
     public static String InterpreterRegistry_sessionNotFoundErrorMsg;
+    
+    @TranslatableMessage
+    public static String InterpretedExpressionQueryProviderRegistry_instanciationError;
 
     @TranslatableMessage
     public static String InterpreterRegistry_nullModelElementErrorMsg;
diff --git a/plugins/org.eclipse.sirius/src/org/eclipse/sirius/viewpoint/SiriusPlugin.java b/plugins/org.eclipse.sirius/src/org/eclipse/sirius/viewpoint/SiriusPlugin.java
index d516c8d901..ec02b97f64 100644
--- a/plugins/org.eclipse.sirius/src/org/eclipse/sirius/viewpoint/SiriusPlugin.java
+++ b/plugins/org.eclipse.sirius/src/org/eclipse/sirius/viewpoint/SiriusPlugin.java
@@ -10,6 +10,8 @@
  *******************************************************************************/
 package org.eclipse.sirius.viewpoint;
 
+import java.util.Collection;
+
 import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.Platform;
@@ -19,8 +21,10 @@ import org.eclipse.emf.common.util.ResourceLocator;
 import org.eclipse.emf.ecore.EValidator;
 import org.eclipse.emf.ecore.plugin.EcorePlugin;
 import org.eclipse.sirius.business.api.componentization.ViewpointRegistry;
+import org.eclipse.sirius.business.api.dialect.description.IInterpretedExpressionQueryProvider;
 import org.eclipse.sirius.business.api.dialect.description.MultiLanguagesValidator;
 import org.eclipse.sirius.business.api.helper.SiriusUtil;
+import org.eclipse.sirius.business.internal.dialect.description.InterpretedExpressionQueryProviderRegistry;
 import org.eclipse.sirius.business.internal.helper.delete.DeleteHookDescriptorRegistryListener;
 import org.eclipse.sirius.business.internal.resource.strategy.ResourceStrategyRegistryListener;
 import org.eclipse.sirius.business.internal.session.factory.SessionFactoryRegistryListener;
@@ -69,7 +73,6 @@ public final class SiriusPlugin extends EMFPlugin {
      */
     private static final ModelAccessorsRegistry REGISTRY = new ModelAccessorsRegistry(SiriusUtil.DESCRIPTION_MODEL_EXTENSION);
 
-
     /**
      * Creates the instance.
      */
@@ -130,6 +133,11 @@ public final class SiriusPlugin extends EMFPlugin {
         private ResourceStrategyRegistryListener resourceStrategyRegistryListener;
 
         /**
+         * The registry for {@link IInterpretedExpressionQueryProvider}.
+         */
+        private InterpretedExpressionQueryProviderRegistry expressionQueryProviderRegistry;
+
+        /**
          * Creates an instance.
          */
         public Implementation() {
@@ -155,6 +163,17 @@ public final class SiriusPlugin extends EMFPlugin {
             javaActionRegistryListener.init();
             resourceStrategyRegistryListener = new ResourceStrategyRegistryListener();
             resourceStrategyRegistryListener.init();
+            expressionQueryProviderRegistry = new InterpretedExpressionQueryProviderRegistry(Platform.getExtensionRegistry(), this);
+            expressionQueryProviderRegistry.init();
+        }
+
+        /**
+         * Returns all the registered IInterpretedExpressionQueryProvider.
+         * 
+         * @return the registered IInterpretedExpressionQueryProvider.
+         */
+        public Collection<IInterpretedExpressionQueryProvider> getInterpretedExpressionQueryProviders() {
+            return expressionQueryProviderRegistry.getEntries();
         }
 
         @Override
@@ -169,6 +188,8 @@ public final class SiriusPlugin extends EMFPlugin {
             javaActionRegistryListener = null;
             resourceStrategyRegistryListener.dispose();
             resourceStrategyRegistryListener = null;
+            expressionQueryProviderRegistry.dispose();
+            expressionQueryProviderRegistry = null;
 
             ViewpointRegistry.getInstance().dispose();