diff --git a/SysML2.NET.Tests/Extend/TextualRepresentationExtensionsTestFixture.cs b/SysML2.NET.Tests/Extend/TextualRepresentationExtensionsTestFixture.cs
index 3ad1b7d9..984a8618 100644
--- a/SysML2.NET.Tests/Extend/TextualRepresentationExtensionsTestFixture.cs
+++ b/SysML2.NET.Tests/Extend/TextualRepresentationExtensionsTestFixture.cs
@@ -1,38 +1,55 @@
-// -------------------------------------------------------------------------------------------------
+// -------------------------------------------------------------------------------------------------
 // <copyright file="TextualRepresentationExtensionsTestFixture.cs" company="Starion Group S.A.">
-// 
+//
 //   Copyright 2022-2026 Starion Group S.A.
-// 
+//
 //   Licensed under the Apache License, Version 2.0 (the "License");
 //   you may not use this file except in compliance with the License.
 //   You may obtain a copy of the License at
-// 
+//
 //        http://www.apache.org/licenses/LICENSE-2.0
-// 
+//
 //    Unless required by applicable law or agreed to in writing, software
 //    distributed under the License is distributed on an "AS IS" BASIS,
 //    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 //    See the License for the specific language governing permissions and
 //    limitations under the License.
-// 
+//
 // </copyright>
 // ------------------------------------------------------------------------------------------------
 
 namespace SysML2.NET.Tests.Extend
 {
     using System;
-    
+
     using NUnit.Framework;
-    
+
     using SysML2.NET.Core.POCO.Root.Annotations;
+    using SysML2.NET.Core.POCO.Systems.DefinitionAndUsage;
+    using SysML2.NET.Exceptions;
+    using SysML2.NET.Extensions;
 
     [TestFixture]
     public class TextualRepresentationExtensionsTestFixture
     {
         [Test]
-        public void ComputeRepresentedElement_ThrowsNotSupportedException()
+        public void VerifyComputeRepresentedElement()
         {
-            Assert.That(() => ((ITextualRepresentation)null).ComputeRepresentedElement(), Throws.TypeOf<NotSupportedException>());
+            Assert.That(() => ((ITextualRepresentation)null).ComputeRepresentedElement(),
+                Throws.TypeOf<ArgumentNullException>());
+
+            var emptyTextualRep = new TextualRepresentation();
+
+            Assert.That(() => emptyTextualRep.ComputeRepresentedElement(),
+                Throws.TypeOf<IncompleteModelException>());
+
+            var target = new Definition();
+            var textualRep = new TextualRepresentation();
+            var annotation = new Annotation();
+
+            target.AssignOwnership(annotation, textualRep);
+
+            Assert.That(textualRep.ComputeRepresentedElement(), Is.SameAs(target));
         }
     }
 }
diff --git a/SysML2.NET/Extend/TextualRepresentationExtensions.cs b/SysML2.NET/Extend/TextualRepresentationExtensions.cs
index fce6d2c3..786f4121 100644
--- a/SysML2.NET/Extend/TextualRepresentationExtensions.cs
+++ b/SysML2.NET/Extend/TextualRepresentationExtensions.cs
@@ -1,4 +1,4 @@
-// -------------------------------------------------------------------------------------------------
+// -------------------------------------------------------------------------------------------------
 // <copyright file="TextualRepresentationExtensions.cs" company="Starion Group S.A.">
 //
 //    Copyright (C) 2022-2026 Starion Group S.A.
@@ -21,10 +21,9 @@
 namespace SysML2.NET.Core.POCO.Root.Annotations
 {
     using System;
-    using System.Collections.Generic;
 
     using SysML2.NET.Core.POCO.Root.Elements;
-    using SysML2.NET.Core.POCO.Root.Namespaces;
+    using SysML2.NET.Exceptions;
 
     /// <summary>
     /// The <see cref="TextualRepresentationExtensions"/> class provides extensions methods for
@@ -33,19 +32,35 @@ namespace SysML2.NET.Core.POCO.Root.Annotations
     internal static class TextualRepresentationExtensions
     {
         /// <summary>
-        /// Computes the derived property.
+        /// Computes the derived <c>representedElement</c> property of a <see cref="ITextualRepresentation"/>.
         /// </summary>
         /// <param name="textualRepresentationSubject">
         /// The subject <see cref="ITextualRepresentation"/>
         /// </param>
         /// <returns>
-        /// the computed result
+        /// The <see cref="IElement"/> that owns this <see cref="ITextualRepresentation"/>,
+        /// which is the <c>representedElement</c>.
         /// </returns>
-        [System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
+        /// <remarks>
+        /// The representedElement must be the owner of the TextualRepresentation
+        /// (OMG KerML spec: representedElement redefines owner, narrowing cardinality to 1..1).
+        /// </remarks>
+        /// <exception cref="ArgumentNullException">
+        /// Thrown when <paramref name="textualRepresentationSubject"/> is <see langword="null"/>.
+        /// </exception>
+        /// <exception cref="IncompleteModelException">
+        /// Thrown when the <see cref="ITextualRepresentation"/> has no owner.
+        /// </exception>
         internal static IElement ComputeRepresentedElement(this ITextualRepresentation textualRepresentationSubject)
         {
-            throw new NotSupportedException("Create a GitHub issue when this method is required");
-        }
+            if (textualRepresentationSubject == null)
+            {
+                throw new ArgumentNullException(nameof(textualRepresentationSubject));
+            }
 
+            return textualRepresentationSubject.owner
+                ?? throw new IncompleteModelException(
+                    $"{nameof(textualRepresentationSubject)} must have an owner (its representedElement)");
+        }
     }
 }