eclipse-syson · AxelRICHARD · Dec 19, 2025
diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
@@ -45,6 +45,7 @@ This fix ensure that imported models containing, for example, a top-level `Libra
 A new compartment named _satisfy requirements_ has also been added to `PartDefinition` and `PartUsage` graphical nodes in diagrams.
 - https://github.com/eclipse-syson/syson/issues/1762[#1762] [diagrams] Increase the default size of nodes.
 - https://github.com/eclipse-syson/syson/issues/1752[#1752] [diagrams] In diagrams, hide the node displayed on the top of the diagram if the candidate compartment is not hidden.
+- https://github.com/eclipse-syson/syson/issues/1778[#1778] [diagrams] Add new `ReferenceSubsetting` tool to create `ReferenceSubsetting` relationships between `Usage` elements in diagrams.
 
 === New features
 

diff --git a/...rc/main/java/org/eclipse/syson/application/configuration/SysMLv2PropertiesConfigurer.java b/...rc/main/java/org/eclipse/syson/application/configuration/SysMLv2PropertiesConfigurer.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2023, 2025 Obeo.
+ * Copyright (c) 2023, 2026 Obeo.
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v2.0
  * which accompanies this distribution, and is available at
@@ -83,6 +83,8 @@ public class SysMLv2PropertiesConfigurer implements IPropertiesDescriptionRegist
 
     private static final String ADVANCED_PROPERTIES = "Advanced Properties";
 
+    private static final String REFERENCE_SUBSETTING_PROPERTIES = "Reference Subsetting Properties";
+
     private static final String REDEFINITION_PROPERTIES = "Redefinition Properties";
 
     private static final String SUBCLASSIFICATION_PROPERTIES = "Subclassification Properties";
@@ -176,6 +178,7 @@ private FormDescription createDetailsViewForElement() {
         pageCore.setLabelExpression("Core");
         pageCore.getGroups().add(this.createCorePropertiesGroup());
         pageCore.getGroups().add(this.createVisibilityPropertyGroup());
+        pageCore.getGroups().add(this.createExtraReferenceSubsettingPropertiesGroup());
         pageCore.getGroups().add(this.createExtraRedefinitionPropertiesGroup());
         pageCore.getGroups().add(this.createExtraStatesubactionMembershipKindPropertiesGroup());
         pageCore.getGroups().add(this.createExtraSubclassificationPropertiesGroup());
@@ -273,6 +276,31 @@ private GroupDescription createExtraRedefinitionPropertiesGroup() {
         return group;
     }
 
+    // should handle multiple ReferenceSubsetting
+    private GroupDescription createExtraReferenceSubsettingPropertiesGroup() {
+        GroupDescription group = FormFactory.eINSTANCE.createGroupDescription();
+        group.setDisplayMode(GroupDisplayMode.LIST);
+        group.setName(REFERENCE_SUBSETTING_PROPERTIES);
+        group.setLabelExpression("");
+        group.setSemanticCandidatesExpression("aql:self.ownedRelationship->filter(sysml::ReferenceSubsetting)");
+
+        ReferenceWidgetDescription refWidget = ReferenceFactory.eINSTANCE.createReferenceWidgetDescription();
+        refWidget.setName("ExtraReferenceWidget");
+        refWidget.setLabelExpression("References");
+        refWidget.setReferenceNameExpression(SysmlPackage.eINSTANCE.getReferenceSubsetting_ReferencedFeature().getName());
+        refWidget.setReferenceOwnerExpression(AQLConstants.AQL_SELF);
+        refWidget.setIsEnabledExpression(AQL_NOT_SELF_IS_READ_ONLY);
+        ChangeContext setRefWidget = ViewFactory.eINSTANCE.createChangeContext();
+        setRefWidget
+                .setExpression("aql:self.handleReferenceWidgetNewValue('" + SysmlPackage.eINSTANCE.getReferenceSubsetting_ReferencedFeature().getName() + "', " + ViewFormDescriptionConverter.NEW_VALUE
+                + LabelConstants.CLOSE_PARENTHESIS);
+        refWidget.getBody().add(setRefWidget);
+
+        group.getChildren().add(refWidget);
+
+        return group;
+    }
+
     private GroupDescription createExtraStatesubactionMembershipKindPropertiesGroup() {
         GroupDescription group = FormFactory.eINSTANCE.createGroupDescription();
         group.setDisplayMode(GroupDisplayMode.LIST);

diff --git a/...onfiguration/src/main/java/org/eclipse/syson/application/services/DetailsViewService.java b/...onfiguration/src/main/java/org/eclipse/syson/application/services/DetailsViewService.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2023, 2025 Obeo.
+ * Copyright (c) 2023, 2026 Obeo.
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v2.0
  * which accompanies this distribution, and is available at
@@ -36,8 +36,8 @@
 import org.eclipse.sirius.components.core.api.IReadOnlyObjectPredicate;
 import org.eclipse.sirius.components.representations.Message;
 import org.eclipse.sirius.components.representations.MessageLevel;
-import org.eclipse.syson.form.services.api.IDetailsViewHelpTextProvider;
 import org.eclipse.syson.application.configuration.SysMLv2PropertiesConfigurer;
+import org.eclipse.syson.form.services.api.IDetailsViewHelpTextProvider;
 import org.eclipse.syson.services.ElementInitializerSwitch;
 import org.eclipse.syson.services.ImportService;
 import org.eclipse.syson.services.UtilService;
@@ -670,6 +670,8 @@ private void handleImplied(Element element, EStructuralFeature eStructuralFeatur
         if (element instanceof Relationship relationship) {
             if (SysmlPackage.eINSTANCE.getRedefinition_RedefinedFeature().equals(eStructuralFeature)) {
                 relationship.setIsImplied(false);
+            } else if (SysmlPackage.eINSTANCE.getReferenceSubsetting_ReferencedFeature().equals(eStructuralFeature)) {
+                relationship.setIsImplied(false);
             } else if (SysmlPackage.eINSTANCE.getSubsetting_SubsettedFeature().equals(eStructuralFeature)) {
                 relationship.setIsImplied(false);
             } else if (SysmlPackage.eINSTANCE.getSubclassification_Superclassifier().equals(eStructuralFeature)) {

diff --git a/...guration/src/main/java/org/eclipse/syson/application/services/GetChildCreationSwitch.java b/...guration/src/main/java/org/eclipse/syson/application/services/GetChildCreationSwitch.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2024, 2025 Obeo.
+ * Copyright (c) 2024, 2026 Obeo.
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v2.0
  * which accompanies this distribution, and is available at
@@ -242,6 +242,7 @@ public List<EClass> caseUsage(Usage object) {
         childrenCandidates.add(SysmlPackage.eINSTANCE.getFeatureTyping());
         childrenCandidates.add(SysmlPackage.eINSTANCE.getSubsetting());
         childrenCandidates.add(SysmlPackage.eINSTANCE.getRedefinition());
+        childrenCandidates.add(SysmlPackage.eINSTANCE.getReferenceSubsetting());
         childrenCandidates.add(SysmlPackage.eINSTANCE.getLiteralBoolean());
         childrenCandidates.add(SysmlPackage.eINSTANCE.getLiteralInfinity());
         childrenCandidates.add(SysmlPackage.eINSTANCE.getLiteralInteger());

diff --git a/backend/application/syson-application/README.md b/backend/application/syson-application/README.md
@@ -2,13 +2,17 @@
 
 ## Developer testing environment
 
-SysON contains tests that can be executed out of the box. The instructions below detail how to configure your development environment to contribute/modify tests and their baseline models.
+SysON contains tests that can be executed out of the box.
+The instructions below detail how to configure your development environment to contribute/modify tests and their baseline models.
 
 ### Prerequisites
 
-The scripts used in the instructions below rely on the `pg_dump` and `psql` executables. We recommand to install [pgAdmin](https://www.pgadmin.org/download/) to get them as well as additional tools to manipulate Postgres databases.
+The scripts used in the instructions below rely on the `pg_dump` and `psql` executables.
+We recommand to install [pgAdmin](https://www.pgadmin.org/download/) to get them as well as additional tools to manipulate Postgres databases.
 
-The scripts below have been tested with Git Bash on Windows. They rely on `winpty` to communicate with Windows console programs. Please adapt the scripts if you are using a different shell/operating system.
+The scripts below must be adapted when using Git Bash on Windows.
+In this case they rely on `winpty` to communicate with Windows console programs.
+Please adapt the scripts if you are using Git Bash on Windows (just comment/uncomment appropriate line in the scripts).
 
 ### Setup the testing environment
 
@@ -33,7 +37,8 @@ docker run -p 5433:5432 --name syson-test-postgres \
 
 2. Start SysON backend & frontend
 
-This creates the database tables required by the tests. The SysON frontend can be used later to update the test models.
+This creates the database tables required by the tests.
+The SysON frontend can be used later to update the test models.
 
 3. Run the initialization script
 

diff --git a/...se/syson/application/controllers/diagrams/general/view/GVEdgeReferenceSubsettingTest.java b/...se/syson/application/controllers/diagrams/general/view/GVEdgeReferenceSubsettingTest.java
@@ -0,0 +1,133 @@
+/*******************************************************************************
+ * Copyright (c) 2026 Obeo.
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.syson.application.controllers.diagrams.general.view;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.eclipse.sirius.components.diagrams.tests.DiagramEventPayloadConsumer.assertRefreshedDiagramThat;
+
+import java.time.Duration;
+import java.util.UUID;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Consumer;
+
+import org.eclipse.sirius.components.collaborative.diagrams.dto.DiagramEventInput;
+import org.eclipse.sirius.components.collaborative.diagrams.dto.DiagramRefreshedEventPayload;
+import org.eclipse.sirius.components.diagrams.Diagram;
+import org.eclipse.sirius.components.diagrams.tests.navigation.DiagramNavigator;
+import org.eclipse.sirius.components.view.emf.diagram.IDiagramIdProvider;
+import org.eclipse.sirius.web.tests.services.api.IGivenInitialServerState;
+import org.eclipse.syson.AbstractIntegrationTests;
+import org.eclipse.syson.application.controllers.diagrams.testers.EdgeCreationTester;
+import org.eclipse.syson.application.data.GeneralViewWithTopNodesTestProjectData;
+import org.eclipse.syson.services.diagrams.DiagramDescriptionIdProvider;
+import org.eclipse.syson.services.diagrams.api.IGivenDiagramDescription;
+import org.eclipse.syson.services.diagrams.api.IGivenDiagramSubscription;
+import org.eclipse.syson.standard.diagrams.view.SDVDescriptionNameGenerator;
+import org.eclipse.syson.sysml.SysmlPackage;
+import org.eclipse.syson.util.IDescriptionNameGenerator;
+import org.eclipse.syson.util.SysONRepresentationDescriptionIdentifiers;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.jdbc.Sql;
+import org.springframework.test.context.jdbc.SqlConfig;
+import org.springframework.transaction.annotation.Transactional;
+
+import reactor.core.publisher.Flux;
+import reactor.test.StepVerifier;
+
+/**
+ * ReferenceSubsetting-Edge related tests the in the General View diagram.
+ *
+ * @author arichard
+ */
+@Transactional
+@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
+public class GVEdgeReferenceSubsettingTest extends AbstractIntegrationTests {
+
+    @Autowired
+    private IGivenInitialServerState givenInitialServerState;
+
+    @Autowired
+    private IGivenDiagramSubscription givenDiagramSubscription;
+
+    @Autowired
+    private IGivenDiagramDescription givenDiagramDescription;
+
+    @Autowired
+    private IDiagramIdProvider diagramIdProvider;
+
+    @Autowired
+    private EdgeCreationTester edgeTester;
+
+    private final IDescriptionNameGenerator descriptionNameGenerator = new SDVDescriptionNameGenerator();
+
+    private Flux<DiagramRefreshedEventPayload> givenSubscriptionToDiagram() {
+        var diagramEventInput = new DiagramEventInput(UUID.randomUUID(),
+                GeneralViewWithTopNodesTestProjectData.EDITING_CONTEXT_ID,
+                GeneralViewWithTopNodesTestProjectData.GraphicalIds.DIAGRAM_ID);
+        var flux = this.givenDiagramSubscription.subscribe(diagramEventInput);
+        return flux;
+    }
+
+    @BeforeEach
+    public void beforeEach() {
+        this.givenInitialServerState.initialize();
+    }
+
+    @DisplayName("GIVEN a diagram with two Usage nodes, WHEN a ReferenceSubsetting edge is created between them, THEN the edge is visisble on the diagram")
+    @Sql(scripts = { GeneralViewWithTopNodesTestProjectData.SCRIPT_PATH }, executionPhase = Sql.ExecutionPhase.BEFORE_TEST_METHOD,
+            config = @SqlConfig(transactionMode = SqlConfig.TransactionMode.ISOLATED))
+    @Sql(scripts = { "/scripts/cleanup.sql" }, executionPhase = Sql.ExecutionPhase.AFTER_TEST_METHOD, config = @SqlConfig(transactionMode = SqlConfig.TransactionMode.ISOLATED))
+    @Test
+    public void testCreateReferenceSubsettingEdge() {
+        var flux = this.givenSubscriptionToDiagram();
+
+        var diagramDescription = this.givenDiagramDescription.getDiagramDescription(GeneralViewWithTopNodesTestProjectData.EDITING_CONTEXT_ID,
+                SysONRepresentationDescriptionIdentifiers.GENERAL_VIEW_DIAGRAM_DESCRIPTION_ID);
+        var diagramDescriptionIdProvider = new DiagramDescriptionIdProvider(diagramDescription, this.diagramIdProvider);
+
+        var newReferenceSubsettingToolId = diagramDescriptionIdProvider.getEdgeCreationToolId(this.descriptionNameGenerator.getNodeName(SysmlPackage.eINSTANCE.getActionUsage()),
+                "New Reference Subsetting");
+        assertThat(newReferenceSubsettingToolId).as("The tool 'New Reference Subsetting' should exist on the ActionUsage").isNotNull();
+
+        var diagram = new AtomicReference<Diagram>();
+
+        Consumer<Object> initialDiagramContentConsumer = assertRefreshedDiagramThat(diag -> {
+            diagram.set(diag);
+            assertThat(new DiagramNavigator(diag).findDiagramEdgeCount()).isEqualTo(3);
+        });
+
+        Runnable newReferenceSubsettingTool = () -> this.edgeTester.createEdgeUsingNodeId(GeneralViewWithTopNodesTestProjectData.EDITING_CONTEXT_ID, diagram,
+                GeneralViewWithTopNodesTestProjectData.GraphicalIds.ACTION_USAGE_ID, GeneralViewWithTopNodesTestProjectData.GraphicalIds.STATE_USAGE_ID, newReferenceSubsettingToolId);
+
+        Consumer<Object> updatedDiagramContentConsumer = assertRefreshedDiagramThat(diag -> {
+            var diagramNavigator = new DiagramNavigator(diag);
+            assertThat(diagramNavigator.findDiagramEdgeCount()).isEqualTo(4);
+            var edgeDescriptionId = diagramDescriptionIdProvider.getEdgeDescriptionId(this.descriptionNameGenerator.getEdgeName(SysmlPackage.eINSTANCE.getReferenceSubsetting()));
+            var referenceSubsettingEdge = diagramNavigator.edgeWithEdgeDescriptionId(edgeDescriptionId).getEdge();
+            assertThat(referenceSubsettingEdge).isNotNull();
+            assertThat(referenceSubsettingEdge.getSourceId()).isEqualTo(GeneralViewWithTopNodesTestProjectData.GraphicalIds.ACTION_USAGE_ID);
+            assertThat(referenceSubsettingEdge.getTargetId()).isEqualTo(GeneralViewWithTopNodesTestProjectData.GraphicalIds.STATE_USAGE_ID);
+        });
+
+        StepVerifier.create(flux)
+                .consumeNextWith(initialDiagramContentConsumer)
+                .then(newReferenceSubsettingTool)
+                .consumeNextWith(updatedDiagramContentConsumer)
+                .thenCancel()
+                .verify(Duration.ofSeconds(10));
+    }
+}
diff --git a/...syson/application/controllers/diagrams/general/view/GVSubNodeActionFlowCreationTests.java b/...syson/application/controllers/diagrams/general/view/GVSubNodeActionFlowCreationTests.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2024, 2025 Obeo.
+ * Copyright (c) 2024, 2026 Obeo.
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v2.0
  * which accompanies this distribution, and is available at
@@ -245,7 +245,7 @@ public void setUp() {
     public void tearDown() {
         if (this.verifier != null) {
             this.verifier.thenCancel()
-                    .verify(Duration.ofSeconds(10));
+                    .verify(Duration.ofSeconds(1000));
         }
     }
 
@@ -561,11 +561,10 @@ public void createReferencingPerformActionUsageInActionUsage() {
         this.creationTestsService.createNode(this.verifier, this.diagramDescriptionIdProvider, this.diagram, parentEClass, parentLabel, creationToolName, variables);
 
         IDiagramChecker diagramChecker = (initialDiagram, newDiagram) -> {
-            int createdNodesExpectedCount = 14;
             new CheckDiagramElementCount(this.diagramComparator)
-                    .hasNewNodeCount(createdNodesExpectedCount)
-                    .hasNewEdgeCount(1)
-                    .check(initialDiagram, newDiagram);
+                    .hasNewNodeCount(1) // 1 visible new PerformActionUsage node
+                    .hasNewEdgeCount(2) // 1 visible composition edge and 1 visible ReferenceSubsetting edge
+                    .check(initialDiagram, newDiagram, true);
             String listNodeDescription = this.descriptionNameGenerator.getCompartmentItemName(parentEClass, containmentReference);
             new CheckNodeInCompartment(this.diagramDescriptionIdProvider, this.diagramComparator)
                     .withParentLabel(parentLabel)

diff --git a/.../test/java/org/eclipse/syson/application/data/GeneralViewWithTopNodesTestProjectData.java b/.../test/java/org/eclipse/syson/application/data/GeneralViewWithTopNodesTestProjectData.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2025 Obeo.
+ * Copyright (c) 2025, 2026 Obeo.
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v2.0
  * which accompanies this distribution, and is available at
@@ -35,6 +35,10 @@ public static class GraphicalIds {
         public static final String PART_DEFINITION_ID = "fa617798-658e-3812-92f2-52e2fc39f851";
 
         public static final String PART_DEFINITION_TEXTUAL_REP_ID = "3a992e49-95fa-384a-bb54-47284825bf17";
+
+        public static final String ACTION_USAGE_ID = "61aaf64a-4fbc-356e-ba73-4bd47b386989";
+
+        public static final String STATE_USAGE_ID = "1541c013-2cc7-3dd7-a39f-6e33d07b411e";
     }
 
     /**