diff --git a/SysML2.NET.Tests/Extend/MetadataFeatureExtensionsTestFixture.cs b/SysML2.NET.Tests/Extend/MetadataFeatureExtensionsTestFixture.cs
index 6223faab..841f9527 100644
--- a/SysML2.NET.Tests/Extend/MetadataFeatureExtensionsTestFixture.cs
+++ b/SysML2.NET.Tests/Extend/MetadataFeatureExtensionsTestFixture.cs
@@ -1,38 +1,211 @@
-// -------------------------------------------------------------------------------------------------
+// -------------------------------------------------------------------------------------------------
 // <copyright file="MetadataFeatureExtensionsTestFixture.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.Core.Features;
+    using SysML2.NET.Core.POCO.Core.Types;
+    using SysML2.NET.Core.POCO.Kernel.FeatureValues;
+    using SysML2.NET.Core.POCO.Kernel.Functions;
     using SysML2.NET.Core.POCO.Kernel.Metadata;
+    using SysML2.NET.Extensions;
 
     [TestFixture]
     public class MetadataFeatureExtensionsTestFixture
     {
         [Test]
-        public void ComputeMetaclass_ThrowsNotSupportedException()
+        public void VerifyComputeMetaclass()
+        {
+            Assert.That(() => ((IMetadataFeature)null).ComputeMetaclass(), Throws.TypeOf<ArgumentNullException>());
+
+            var metadataFeature = new MetadataFeature();
+
+            // Empty: no FeatureTyping → null.
+            Assert.That(metadataFeature.ComputeMetaclass(), Is.Null);
+
+            // Negative: FeatureTyping pointing at a non-Metaclass Type → null.
+            var nonMetaclassType = new FeatureTyping { Type = new Feature() };
+            metadataFeature.AssignOwnership(nonMetaclassType);
+
+            Assert.That(metadataFeature.ComputeMetaclass(), Is.Null);
+
+            // Positive: FeatureTyping pointing at a Metaclass → returned.
+            var metaclass1 = new Metaclass();
+            var typingToMetaclass1 = new FeatureTyping { Type = metaclass1 };
+            metadataFeature.AssignOwnership(typingToMetaclass1);
+
+            Assert.That(metadataFeature.ComputeMetaclass(), Is.SameAs(metaclass1));
+
+            // Multiple Metaclass typings → first returned (insertion order).
+            var metaclass2 = new Metaclass();
+            var typingToMetaclass2 = new FeatureTyping { Type = metaclass2 };
+            metadataFeature.AssignOwnership(typingToMetaclass2);
+
+            Assert.That(metadataFeature.ComputeMetaclass(), Is.SameAs(metaclass1));
+        }
+
+        [Test]
+        public void VerifyComputeEvaluateFeatureOperation()
+        {
+            // Null guard on subject.
+            Assert.That(() => ((IMetadataFeature)null).ComputeEvaluateFeatureOperation(new Feature()), Throws.TypeOf<ArgumentNullException>());
+
+            var metadataFeature = new MetadataFeature();
+            var baseFeature = new Feature();
+
+            // Null baseFeature: throws ArgumentNullException (matching subject null-guard convention).
+            Assert.That(() => metadataFeature.ComputeEvaluateFeatureOperation(null), Throws.TypeOf<ArgumentNullException>());
+
+            // Empty feature list: MetadataFeature with no feature members → [].
+            Assert.That(metadataFeature.ComputeEvaluateFeatureOperation(baseFeature), Is.Empty);
+
+            // Negative discrimination: feature present whose redefinition closure does NOT include baseFeature → [].
+            var unrelatedFeature = new Feature();
+            var unrelatedMembership = new FeatureMembership();
+            metadataFeature.AssignOwnership(unrelatedMembership, unrelatedFeature);
+
+            Assert.That(metadataFeature.ComputeEvaluateFeatureOperation(baseFeature), Is.Empty);
+
+            // Direct match: candidate IS baseFeature (closure includes start node).
+            // No FeatureValue owned by the closure → returns [].
+            var metadataFeature2 = new MetadataFeature();
+            var directMembership = new FeatureMembership();
+            metadataFeature2.AssignOwnership(directMembership, baseFeature);
+
+            Assert.That(metadataFeature2.ComputeEvaluateFeatureOperation(baseFeature), Is.Empty);
+
+            // Transitive match: candidate redefines baseFeature via a one-step chain.
+            // No FeatureValue → still returns [].
+            var metadataFeature3 = new MetadataFeature();
+            var transitiveCandidate = new Feature();
+            var transitiveRedefinition = new Redefinition { RedefinedFeature = baseFeature };
+            transitiveCandidate.AssignOwnership(transitiveRedefinition);
+
+            var transitiveMembership = new FeatureMembership();
+            metadataFeature3.AssignOwnership(transitiveMembership, transitiveCandidate);
+
+            Assert.That(metadataFeature3.ComputeEvaluateFeatureOperation(baseFeature), Is.Empty);
+
+            // Cycle test: featureA.ownedRedefinition → featureB, featureB.ownedRedefinition → featureA.
+            // Closure helper must terminate; if the cycle does not include baseFeature → [].
+            var metadataFeature4 = new MetadataFeature();
+            var cycleFeatureA = new Feature();
+            var cycleFeatureB = new Feature();
+
+            var redefinitionAtoB = new Redefinition { RedefinedFeature = cycleFeatureB };
+            cycleFeatureA.AssignOwnership(redefinitionAtoB);
+
+            var redefinitionBtoA = new Redefinition { RedefinedFeature = cycleFeatureA };
+            cycleFeatureB.AssignOwnership(redefinitionBtoA);
+
+            var cycleMembership = new FeatureMembership();
+            metadataFeature4.AssignOwnership(cycleMembership, cycleFeatureA);
+
+            // Must not throw or infinite-loop; cycle does not include baseFeature → terminates with [].
+            Assert.That(() => metadataFeature4.ComputeEvaluateFeatureOperation(baseFeature), Throws.Nothing);
+            Assert.That(metadataFeature4.ComputeEvaluateFeatureOperation(baseFeature), Is.Empty);
+
+            // Matched candidate with a FeatureValue whose value is a non-null Expression that has
+            // NO ResultExpressionMembership wired. Expression.Evaluate returns an empty list, so
+            // the operation returns the same empty list. (The stub-blocker case where Evaluate
+            // throws NotSupportedException via ResultExpressionMembershipExtensions.ComputeOwnedResultExpression
+            // cannot be wired here without modifying the sibling stub — scope discipline.)
+            var metadataFeature5 = new MetadataFeature();
+            var matchingFeature = new Feature();
+            var redefinitionToBase = new Redefinition { RedefinedFeature = baseFeature };
+            matchingFeature.AssignOwnership(redefinitionToBase);
+
+            var featureValue = new FeatureValue();
+            var valueExpression = new Expression();
+            matchingFeature.AssignOwnership(featureValue, valueExpression);
+
+            var matchingMembership = new FeatureMembership();
+            metadataFeature5.AssignOwnership(matchingMembership, matchingFeature);
+
+            Assert.That(metadataFeature5.ComputeEvaluateFeatureOperation(baseFeature), Is.Empty);
+        }
+
+        [Test]
+        public void VerifyComputeIsSemanticOperation()
+        {
+            // Null guard.
+            Assert.That(() => ((IMetadataFeature)null).ComputeIsSemanticOperation(), Throws.TypeOf<ArgumentNullException>());
+
+            var metadataFeature = new MetadataFeature();
+
+            // Empty: no library specialization context → SpecializesFromLibrary("Metaobjects::SemanticMetadata")
+            // resolves to null → returns false.
+            Assert.That(metadataFeature.ComputeIsSemanticOperation(), Is.False);
+
+            // Discrimination: having a supertype that is a different library element still returns false.
+            // Wire a non-SemanticMetadata OwningMembership-contained type so the specialization chain is
+            // present but does not match the "Metaobjects::SemanticMetadata" qualified name.
+            var metadataFeature2 = new MetadataFeature();
+            var unrelatedSupertype = new Feature();
+            var subsetting = new Subsetting { SubsettedFeature = unrelatedSupertype };
+            metadataFeature2.AssignOwnership(subsetting);
+
+            Assert.That(metadataFeature2.ComputeIsSemanticOperation(), Is.False);
+
+            // NOTE: Wiring a true positive (returns true) requires constructing a "Metaobjects::SemanticMetadata"
+            // library namespace reachable via ResolveGlobal, which is infrastructure not available in unit tests.
+            // Integration-level coverage is required for the true-positive path.
+        }
+
+        [Test]
+        public void VerifyComputeIsSyntacticOperation()
+        {
+            // Null guard.
+            Assert.That(() => ((IMetadataFeature)null).ComputeIsSyntacticOperation(), Throws.TypeOf<ArgumentNullException>());
+
+            var metadataFeature = new MetadataFeature();
+
+            // Empty: no library specialization context → SpecializesFromLibrary("KerML::Element")
+            // resolves to null → returns false.
+            Assert.That(metadataFeature.ComputeIsSyntacticOperation(), Is.False);
+
+            // Discrimination: having a supertype that is a different library element still returns false.
+            var metadataFeature2 = new MetadataFeature();
+            var unrelatedSupertype = new Feature();
+            var subsetting = new Subsetting { SubsettedFeature = unrelatedSupertype };
+            metadataFeature2.AssignOwnership(subsetting);
+
+            Assert.That(metadataFeature2.ComputeIsSyntacticOperation(), Is.False);
+
+            // NOTE: Wiring a true positive (returns true) requires constructing a "KerML::Element" library
+            // namespace reachable via ResolveGlobal, which is infrastructure not available in unit tests.
+            // Integration-level coverage is required for the true-positive path.
+        }
+
+        [Test]
+        public void VerifyComputeSyntaxElementOperation_ThrowsNotSupportedException()
         {
-            Assert.That(() => ((IMetadataFeature)null).ComputeMetaclass(), Throws.TypeOf<NotSupportedException>());
+            // Pending MOF reflective metaclass registry. Follow-up issue required.
+            // The KerML spec defines this operation with body "No OCL"; computing syntaxElement requires
+            // an inverse map from a runtime MetadataFeature back to the Element it reflects — infrastructure
+            // that does not yet exist in this SDK.
+            Assert.That(() => new MetadataFeature().ComputeSyntaxElementOperation(), Throws.TypeOf<NotSupportedException>());
         }
     }
 }
diff --git a/SysML2.NET/Extend/MetadataFeatureExtensions.cs b/SysML2.NET/Extend/MetadataFeatureExtensions.cs
index cc84d248..87cc35d6 100644
--- a/SysML2.NET/Extend/MetadataFeatureExtensions.cs
+++ b/SysML2.NET/Extend/MetadataFeatureExtensions.cs
@@ -22,14 +22,11 @@ namespace SysML2.NET.Core.POCO.Kernel.Metadata
 {
     using System;
     using System.Collections.Generic;
+    using System.Linq;
 
-    using SysML2.NET.Core.Core.Types;
-    using SysML2.NET.Core.Root.Namespaces;
     using SysML2.NET.Core.POCO.Core.Features;
-    using SysML2.NET.Core.POCO.Core.Types;
-    using SysML2.NET.Core.POCO.Root.Annotations;
+    using SysML2.NET.Core.POCO.Kernel.FeatureValues;
     using SysML2.NET.Core.POCO.Root.Elements;
-    using SysML2.NET.Core.POCO.Root.Namespaces;
 
     /// <summary>
     /// The <see cref="MetadataFeatureExtensions"/> class provides extensions methods for
@@ -56,10 +53,16 @@ internal static class MetadataFeatureExtensions
         /// <returns>
         /// the computed result
         /// </returns>
-        [System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
         internal static IMetaclass ComputeMetaclass(this IMetadataFeature metadataFeatureSubject)
         {
-            throw new NotSupportedException("Create a GitHub issue when this method is required");
+            if (metadataFeatureSubject == null)
+            {
+                throw new ArgumentNullException(nameof(metadataFeatureSubject));
+            }
+
+            var metaclassTypes = metadataFeatureSubject.type.OfType<IMetaclass>().ToList();
+
+            return metaclassTypes.Count == 0 ? null : metaclassTypes[0];
         }
 
         /// <summary>
@@ -88,15 +91,48 @@ internal static IMetaclass ComputeMetaclass(this IMetadataFeature metadataFeatur
         /// The subject <see cref="IMetadataFeature"/>
         /// </param>
         /// <param name="baseFeature">
-        /// No documentation provided
+        /// The base <see cref="IFeature"/> to look up in the redefinition closure of each feature
+        /// owned by the subject.
         /// </param>
         /// <returns>
         /// The expected collection of <see cref="IElement" />
         /// </returns>
-        [System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
         internal static List<IElement> ComputeEvaluateFeatureOperation(this IMetadataFeature metadataFeatureSubject, IFeature baseFeature)
         {
-            throw new NotSupportedException("Create a GitHub issue when this method is required");
+            if (metadataFeatureSubject == null)
+            {
+                throw new ArgumentNullException(nameof(metadataFeatureSubject));
+            }
+
+            if (baseFeature == null)
+            {
+                throw new ArgumentNullException(nameof(baseFeature));
+            }
+
+            var selectedFeatures = metadataFeatureSubject.feature
+                .Where(feature => ComputeRedefinitionClosure(feature).Contains(baseFeature))
+                .ToList();
+
+            if (selectedFeatures.Count == 0)
+            {
+                return [];
+            }
+
+            var selectedFeature = selectedFeatures[0];
+
+            var featureValues = ComputeRedefinitionClosure(selectedFeature)
+                .SelectMany(feature => feature.ownedMember)
+                .OfType<IFeatureValue>()
+                .ToList();
+
+            if (featureValues.Count == 0)
+            {
+                return [];
+            }
+
+            var valueExpression = featureValues[0].value;
+
+            return valueExpression == null ? [] : valueExpression.Evaluate(metadataFeatureSubject);
         }
 
         /// <summary>
@@ -114,10 +150,11 @@ internal static List<IElement> ComputeEvaluateFeatureOperation(this IMetadataFea
         /// <returns>
         /// The expected <see cref="bool" />
         /// </returns>
-        [System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
         internal static bool ComputeIsSemanticOperation(this IMetadataFeature metadataFeatureSubject)
         {
-            throw new NotSupportedException("Create a GitHub issue when this method is required");
+            return metadataFeatureSubject == null
+                ? throw new ArgumentNullException(nameof(metadataFeatureSubject))
+                : metadataFeatureSubject.SpecializesFromLibrary("Metaobjects::SemanticMetadata");
         }
 
         /// <summary>
@@ -136,10 +173,11 @@ internal static bool ComputeIsSemanticOperation(this IMetadataFeature metadataFe
         /// <returns>
         /// The expected <see cref="bool" />
         /// </returns>
-        [System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
         internal static bool ComputeIsSyntacticOperation(this IMetadataFeature metadataFeatureSubject)
         {
-            throw new NotSupportedException("Create a GitHub issue when this method is required");
+            return metadataFeatureSubject == null
+                ? throw new ArgumentNullException(nameof(metadataFeatureSubject))
+                : metadataFeatureSubject.SpecializesFromLibrary("KerML::Element");
         }
 
         /// <summary>
@@ -165,7 +203,47 @@ internal static bool ComputeIsSyntacticOperation(this IMetadataFeature metadataF
         [System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
         internal static IElement ComputeSyntaxElementOperation(this IMetadataFeature metadataFeatureSubject)
         {
+            // Implementation deferred: requires a MOF reflective metaclass registry
+            // (runtime MetadataFeature -> reflected IElement) that is not present in this SDK.
             throw new NotSupportedException("Create a GitHub issue when this method is required");
         }
+
+        /// <summary>
+        /// Computes the reflexive-transitive closure of <paramref name="start"/> over
+        /// <c>ownedRedefinition.RedefinedFeature</c>, using a HashSet visited-set for cycle protection.
+        /// </summary>
+        /// <param name="start">
+        /// The seed <see cref="IFeature"/> to start the closure from. The seed itself is included in
+        /// the result when non-null.
+        /// </param>
+        /// <returns>
+        /// A fresh <see cref="List{T}"/> containing the seed and all transitively redefined features,
+        /// in BFS order. Returns an empty list when <paramref name="start"/> is null.
+        /// </returns>
+        private static List<IFeature> ComputeRedefinitionClosure(IFeature start)
+        {
+            var visited = new HashSet<IFeature>();
+            var result = new List<IFeature>();
+            var queue = new Queue<IFeature>();
+
+            if (start != null && visited.Add(start))
+            {
+                queue.Enqueue(start);
+                result.Add(start);
+            }
+
+            while (queue.Count > 0)
+            {
+                var current = queue.Dequeue();
+
+                foreach (var redefinedFeature in current.ownedRedefinition.Select(x => x.RedefinedFeature).Where(x => x != null && visited.Add(x)))
+                {
+                    queue.Enqueue(redefinedFeature);
+                    result.Add(redefinedFeature);
+                }
+            }
+
+            return result;
+        }
     }
 }