diff --git a/org.omg.sysml.logic.bundle/lib/org.omg.sysml.logic-0.61.0-SNAPSHOT.jar b/org.omg.sysml.logic.bundle/lib/org.omg.sysml.logic-0.61.0-SNAPSHOT.jar
index 2ef1bdbe0..e7a459d4e 100644
Binary files a/org.omg.sysml.logic.bundle/lib/org.omg.sysml.logic-0.61.0-SNAPSHOT.jar and b/org.omg.sysml.logic.bundle/lib/org.omg.sysml.logic-0.61.0-SNAPSHOT.jar differ
diff --git a/org.omg.sysml.logic/src/main/java/org/omg/sysml/adapter/UsageAdapter.java b/org.omg.sysml.logic/src/main/java/org/omg/sysml/adapter/UsageAdapter.java
index 97f23f2d4..2072d544c 100644
--- a/org.omg.sysml.logic/src/main/java/org/omg/sysml/adapter/UsageAdapter.java
+++ b/org.omg.sysml.logic/src/main/java/org/omg/sysml/adapter/UsageAdapter.java
@@ -1,6 +1,6 @@
 /*******************************************************************************
  * SysML 2 Pilot Implementation
- * Copyright (c) 2021-2025, 2026 Model Driven Solutions, Inc.
+ * Copyright (c) 2021-2026 Model Driven Solutions, Inc.
  *    
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the Eclipse Public License as published by
@@ -22,6 +22,8 @@
 
 import org.omg.sysml.lang.sysml.ActionDefinition;
 import org.omg.sysml.lang.sysml.ActionUsage;
+import org.omg.sysml.lang.sysml.AttributeDefinition;
+import org.omg.sysml.lang.sysml.AttributeUsage;
 import org.omg.sysml.lang.sysml.Definition;
 import org.omg.sysml.lang.sysml.Feature;
 import org.omg.sysml.lang.sysml.FeatureMembership;
@@ -54,6 +56,8 @@ public Usage getTarget() {
 	
 	/**
 	 * @satisfies validateUsageIsReferential
+	 * @satisfies validateAttributeDefinitionFeature
+	 * @satisfies validateAttributeUsageFeature
 	 */
 	@Override
 	public void postProcess () {
@@ -62,7 +66,9 @@ public void postProcess () {
 		if (target.isVariation()) {
 			target.setIsAbstract(true);
 		}
-		if (target.getDirection() != null || target.isEnd() || !UsageUtil.hasFeaturingType(target)) {
+		Type featuringType = UsageUtil.getExpectedFeaturingTypeOf(target);
+		if (target.getDirection() != null || target.isEnd() || featuringType == null ||
+			featuringType instanceof AttributeDefinition || featuringType instanceof AttributeUsage) {
 			target.setIsComposite(false);
 		}
 	}
diff --git a/org.omg.sysml.logic/src/test/java/org/omg/sysml/logic/UsagePostProcessTest.java b/org.omg.sysml.logic/src/test/java/org/omg/sysml/logic/UsagePostProcessTest.java
index db261dac0..065ce7108 100644
--- a/org.omg.sysml.logic/src/test/java/org/omg/sysml/logic/UsagePostProcessTest.java
+++ b/org.omg.sysml.logic/src/test/java/org/omg/sysml/logic/UsagePostProcessTest.java
@@ -28,6 +28,7 @@
 import org.eclipse.emf.ecore.EClass;
 import org.junit.BeforeClass;
 import org.junit.Test;
+import org.omg.sysml.lang.sysml.Definition;
 import org.omg.sysml.lang.sysml.Element;
 import org.omg.sysml.lang.sysml.FeatureDirectionKind;
 import org.omg.sysml.lang.sysml.Namespace;
@@ -70,6 +71,12 @@ public void settingCompositeToFalse() throws InvocationTargetException {
 		 *	   variation part q {
 		 *	       variant part r;
 		 *     }
+		 *     attribute def B {
+		 *         part p1;
+		 *     }
+		 *     attribute b {
+		 *         part p2;
+		 *     }
 		 * }
 		 */
 		Package test = (Package) createElement(SysMLPackage.Literals.PACKAGE, "test", null);
@@ -88,8 +95,15 @@ public void settingCompositeToFalse() throws InvocationTargetException {
 		q.setIsVariation(true);
 		Usage r = (Usage) createElement(SysMLPackage.Literals.PART_USAGE, "r", q);
 		
+		Definition B = SysMLFactory.eINSTANCE.createAttributeDefinition();
+		Usage p1 = SysMLFactory.eINSTANCE.createPartUsage();
+		TypeUtil.addOwnedFeatureTo(B, p1);
+		Usage b = SysMLFactory.eINSTANCE.createAttributeUsage();
+		Usage p2 = SysMLFactory.eINSTANCE.createPartUsage();
+		TypeUtil.addOwnedFeatureTo(b, p2);
+		
 		// Post-process after creating the entire model.
-		postProcess(p, a, x, y, z, u, v, w, q, r);
+		postProcess(p, a, x, y, z, u, v, w, q, r, B, p1, b, p2);
 		
 		assertTrue(p.isReference());
 		assertTrue(a.isReference());
@@ -101,6 +115,10 @@ public void settingCompositeToFalse() throws InvocationTargetException {
 		assertTrue(w.isReference());
 		assertTrue(q.isReference());
 		assertTrue(r.isReference());
+		
+		assertTrue(p1.isReference());
+		assertTrue(b.isReference());
+		assertTrue(p2.isReference());
 	}
 	
 	/**
diff --git a/org.omg.sysml.xtext/src/org/omg/sysml/xtext/validation/SysMLValidator.xtend b/org.omg.sysml.xtext/src/org/omg/sysml/xtext/validation/SysMLValidator.xtend
index a465839e0..cb988f95a 100644
--- a/org.omg.sysml.xtext/src/org/omg/sysml/xtext/validation/SysMLValidator.xtend
+++ b/org.omg.sysml.xtext/src/org/omg/sysml/xtext/validation/SysMLValidator.xtend
@@ -549,11 +549,10 @@ class SysMLValidator extends KerMLValidator {
 
 	@Check
 	def checkAttributeDefinition(AttributeDefinition defn) {
-		// Not implemented for now, until resolution of KerML issues on composite semantics. (See KERML-4.)
-		// TODO: Check validateAttributeDefinitionFeatures
+		// Check validateAttributeDefinitionFeatures
 		// NOTE: Only check owned features, for efficiency and to avoid redundancy.
 		// (This should be sufficient, unless a composite feature is inherited from a KerML data type.)
-		// checkAllNotComposite(defn.ownedFeature, INVALID_ATTRIBUTE_DEFINITION_FEATURES_MSG, INVALID_ATTRIBUTE_DEFINITION_FEATURES)
+		checkAllNotComposite(defn.ownedFeature, INVALID_ATTRIBUTE_DEFINITION_FEATURES_MSG, INVALID_ATTRIBUTE_DEFINITION_FEATURES)
 	}
 	
 	@Check 
@@ -573,11 +572,10 @@ class SysMLValidator extends KerMLValidator {
 			error(INVALID_REFERENCE_USAGE_IS_REFERENCE_MSG, usg, null, INVALID_REFERENCE_USAGE_IS_REFERENCE)
 		}		
 		
-		// Not implemented for now, until resolution of KerML issues on composite semantics. (See KerML-4.)
-		// TODO: Check validateAttributeUsageFeatures
+		// Check validateAttributeUsageFeatures
 		// NOTE: Only check owned features, for efficiency and to avoid redundancy.
 		// (This should be sufficient, unless a composite feature is inherited from a KerML data type.)
-		// checkAllNotComposite(usg.ownedFeature, INVALID_ATTRIBUTE_USAGE_FEATURES_MSG, INVALID_ATTRIBUTE_USAGE_FEATURES)
+		checkAllNotComposite(usg.ownedFeature, INVALID_ATTRIBUTE_USAGE_FEATURES_MSG, INVALID_ATTRIBUTE_USAGE_FEATURES)
 	}
 	
 	@Check
diff --git a/sysml.library/Systems Library/Actions.sysml b/sysml.library/Systems Library/Actions.sysml
index 65a3b108e..cc78878b8 100644
--- a/sysml.library/Systems Library/Actions.sysml	
+++ b/sysml.library/Systems Library/Actions.sysml	
@@ -145,7 +145,13 @@ standard library package Actions {
 			 * The subactions of this Action that are AssignmentActions.
 			 */
 			 
-			 in target;
+			 in target {
+			    doc 
+			    /*
+			     * This provides an implicit redefining feature for AssignmentAction::target and 
+			     * assignmentActions::target, ensuring "target" remains the first parameter.
+			     */
+			}
 		}
 		
 		abstract action ifSubactions : IfThenAction[0..*] :> subactions, ifThenActions {