[507702] Support semantically distinct derived Variable classes

23 files changed, 325 insertions, 221 deletions

diff --git a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/common/AbstractQVTc2QVTc.java b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/common/AbstractQVTc2QVTc.java
index ad678038f..bbdb6bb77 100644
--- a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/common/AbstractQVTc2QVTc.java
+++ b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/common/AbstractQVTc2QVTc.java
@@ -36,6 +36,7 @@ import org.eclipse.ocl.pivot.Operation;
 import org.eclipse.ocl.pivot.OperationCallExp;
 import org.eclipse.ocl.pivot.Package;
 import org.eclipse.ocl.pivot.Parameter;
+import org.eclipse.ocl.pivot.ParameterVariable;
 import org.eclipse.ocl.pivot.PivotFactory;
 import org.eclipse.ocl.pivot.PivotPackage;
 import org.eclipse.ocl.pivot.Property;
@@ -57,9 +58,11 @@ import org.eclipse.qvtd.pivot.qvtbase.Transformation;
 import org.eclipse.qvtd.pivot.qvtbase.TypedModel;
 import org.eclipse.qvtd.pivot.qvtbase.utilities.QVTbaseUtil;
 import org.eclipse.qvtd.pivot.qvtcore.BottomPattern;
+import org.eclipse.qvtd.pivot.qvtcore.BottomVariable;
 import org.eclipse.qvtd.pivot.qvtcore.CoreDomain;
 import org.eclipse.qvtd.pivot.qvtcore.CoreModel;
 import org.eclipse.qvtd.pivot.qvtcore.GuardPattern;
+import org.eclipse.qvtd.pivot.qvtcore.GuardVariable;
 import org.eclipse.qvtd.pivot.qvtcore.Mapping;
 import org.eclipse.qvtd.pivot.qvtcore.NavigationAssignment;
 import org.eclipse.qvtd.pivot.qvtcore.OppositePropertyAssignment;
@@ -178,6 +181,15 @@ public abstract class AbstractQVTc2QVTc
 		}
 
 		@Override
+		public @NonNull BottomVariable visitBottomVariable(@NonNull BottomVariable vIn) {
+			BottomVariable vOut = QVTcoreFactory.eINSTANCE.createBottomVariable();
+			context.addTrace(vIn, vOut);
+			vOut.setName(vIn.getName());
+			createAll(vIn.getOwnedComments(), vOut.getOwnedComments());
+			return vOut;
+		}
+
+		@Override
 		public @Nullable Element visitComment(@NonNull Comment cIn) {
 			Comment cOut = PivotFactory.eINSTANCE.createComment();
 			context.addTrace(cIn, cOut);
@@ -248,6 +260,15 @@ public abstract class AbstractQVTc2QVTc
 		}
 
 		@Override
+		public @NonNull GuardVariable visitGuardVariable(@NonNull GuardVariable vIn) {
+			GuardVariable vOut = QVTcoreFactory.eINSTANCE.createGuardVariable();
+			context.addTrace(vIn, vOut);
+			vOut.setName(vIn.getName());
+			createAll(vIn.getOwnedComments(), vOut.getOwnedComments());
+			return vOut;
+		}
+
+		@Override
 		public @Nullable Element visitImport(@NonNull Import iIn) {
 			Import iOut = context.createImport(iIn);
 			createAll(iIn.getOwnedComments(), iOut.getOwnedComments());
@@ -293,6 +314,15 @@ public abstract class AbstractQVTc2QVTc
 		}
 
 		@Override
+		public @NonNull ParameterVariable visitParameterVariable(@NonNull ParameterVariable vIn) {
+			ParameterVariable vOut = PivotFactory.eINSTANCE.createParameterVariable();
+			context.addTrace(vIn, vOut);
+			vOut.setName(vIn.getName());
+			createAll(vIn.getOwnedComments(), vOut.getOwnedComments());
+			return vOut;
+		}
+
+		@Override
 		public @Nullable Element visitPredicate(@NonNull Predicate pIn) {
 			Predicate pOut = QVTbaseFactory.eINSTANCE.createPredicate();
 			context.addTrace(pIn, pOut);
@@ -353,15 +383,6 @@ public abstract class AbstractQVTc2QVTc
 		}
 
 		@Override
-		public @NonNull Variable visitVariable(@NonNull Variable vIn) {
-			Variable vOut = PivotFactory.eINSTANCE.createVariable();
-			context.addTrace(vIn, vOut);
-			vOut.setName(vIn.getName());
-			createAll(vIn.getOwnedComments(), vOut.getOwnedComments());
-			return vOut;
-		}
-
-		@Override
 		public @Nullable Element visitVariableAssignment(@NonNull VariableAssignment vaIn) {
 			VariableAssignment vaOut = QVTcoreFactory.eINSTANCE.createVariableAssignment();
 			context.addTrace(vaIn, vaOut);
diff --git a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtc2qvtu/QVTc2QVTu.java b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtc2qvtu/QVTc2QVTu.java
index d7b54d3f5..95a3b4e05 100644
--- a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtc2qvtu/QVTc2QVTu.java
+++ b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtc2qvtu/QVTc2QVTu.java
@@ -44,6 +44,7 @@ import org.eclipse.qvtd.pivot.qvtbase.Transformation;
 import org.eclipse.qvtd.pivot.qvtcore.Area;
 import org.eclipse.qvtd.pivot.qvtcore.Assignment;
 import org.eclipse.qvtd.pivot.qvtcore.BottomPattern;
+import org.eclipse.qvtd.pivot.qvtcore.BottomVariable;
 import org.eclipse.qvtd.pivot.qvtcore.CoreDomain;
 import org.eclipse.qvtd.pivot.qvtcore.CoreModel;
 import org.eclipse.qvtd.pivot.qvtcore.CorePattern;
@@ -450,7 +451,7 @@ public class QVTc2QVTu extends AbstractQVTc2QVTc
 		public @NonNull Variable visitRealizedVariable(@NonNull RealizedVariable rvIn) {
 			Area aIn = getContainingArea(rvIn);
 			if (isInputDomain(aIn)) {
-				Variable vOut = PivotFactory.eINSTANCE.createVariable();
+				BottomVariable vOut = QVTcoreFactory.eINSTANCE.createBottomVariable();
 				assert vOut != null;
 				context.addTrace(rvIn, vOut);
 				vOut.setName(rvIn.getName());
diff --git a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtp2qvts/IsConstantExpressionVisitor.java b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtp2qvts/IsConstantExpressionVisitor.java
index d320d4a66..ddce15e9e 100644
--- a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtp2qvts/IsConstantExpressionVisitor.java
+++ b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtp2qvts/IsConstantExpressionVisitor.java
@@ -11,7 +11,6 @@
 package org.eclipse.qvtd.compiler.internal.qvtp2qvts;
 
 import java.util.HashSet;
-import java.util.List;
 import java.util.Set;
 
 import org.eclipse.jdt.annotation.NonNull;
@@ -36,41 +35,44 @@ import org.eclipse.ocl.pivot.TupleLiteralPart;
 import org.eclipse.ocl.pivot.TypeExp;
 import org.eclipse.ocl.pivot.Variable;
 import org.eclipse.ocl.pivot.VariableExp;
-import org.eclipse.ocl.pivot.util.AbstractExtendingVisitor;
 import org.eclipse.ocl.pivot.util.Visitable;
+import org.eclipse.ocl.pivot.utilities.PivotUtil;
+import org.eclipse.qvtd.pivot.qvtcore.util.AbstractExtendingQVTcoreVisitor;
+
+import com.google.common.collect.Iterables;
 
 /**
  * The INSTANCE of the IsConstantExpressionVisitor visits an expression tree to determine whether
  * the tree evaluates to an unconditionally constant value.
- * 
- * Any use of a VariableExp with an indeterminate initializer causes a non-constant verdict. 
- * 
+ *
+ * Any use of a VariableExp with an indeterminate initializer causes a non-constant verdict.
+ *
  * Use of a LoopExp iterator within its loop is constant, provided the loop source is constant.
- * 
+ *
  * Use of NavigationCallExp is constant, provided the navigation source is constant.
- * 
+ *
  * Use of OperationCallExp is constant, provided the source and arguments are constant; OCL has only queries.
  */
-public class IsConstantExpressionVisitor extends AbstractExtendingVisitor<Boolean, Object>
+public class IsConstantExpressionVisitor extends AbstractExtendingQVTcoreVisitor<@NonNull Boolean, @Nullable Object>
 {
 	/**
 	 * Objects (variables) asserted to be constant by the caller.
 	 */
-	protected final @Nullable Set<Object> knownConstants;
+	protected final @Nullable Set<@NonNull Object> knownConstants;
 
 	/**
 	 * Objects (variables) asserted to be constant by the caller or effectively constant as a consequence
 	 * of use within an iteration.
 	 */
-	private /*@LazyNonNull*/ Set<Object> myConstants = null;
+	private /*@LazyNonNull*/ Set<@NonNull Object> myConstants = null;
 
 	/**
 	 * Construct an IsConstantExpressionVisitor that may be used to determine whether expressions
 	 * are constant-valued. If knownConstants is provided any references to them are interpreted
 	 * as constant-valued.
 	 */
-	public IsConstantExpressionVisitor(@Nullable Set<Object> knownConstants) {
-		super(IsConstantExpressionVisitor.class);
+	public IsConstantExpressionVisitor(@Nullable Set<@NonNull Object> knownConstants) {
+		super(null);
 		this.knownConstants = knownConstants;
 	}
 
@@ -145,14 +147,14 @@ public class IsConstantExpressionVisitor extends AbstractExtendingVisitor<Boolea
 		}
 		if (myConstants == null) {
 			if (knownConstants != null) {
-				myConstants = new HashSet<Object>(knownConstants);
+				myConstants = new HashSet<>(knownConstants);
 			}
 			else {
-				myConstants = new HashSet<Object>();
+				myConstants = new HashSet<>();
 			}
 		}
-		List<Variable> ownedIterators = loopExp.getOwnedIterators();
-		myConstants.addAll(ownedIterators);
+		Iterable<@NonNull Variable> ownedIterators = PivotUtil.getOwnedIterators(loopExp);
+		Iterables.addAll(myConstants, ownedIterators);
 		return isConstant(ownedIterators) && isConstant(loopExp.getOwnedBody());
 	}
 
diff --git a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtr2qvtc/CoreVariableAnalysis.java b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtr2qvtc/CoreVariableAnalysis.java
index a3a23daf4..7bc560717 100644
--- a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtr2qvtc/CoreVariableAnalysis.java
+++ b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtr2qvtc/CoreVariableAnalysis.java
@@ -27,7 +27,7 @@ public class CoreVariableAnalysis extends AbstractVariableAnalysis
 
 	public CoreVariableAnalysis(@NonNull VariablesAnalysis variablesAnalysis, @NonNull String name, @NonNull Type type, @Nullable OCLExpression initValue) {
 		super(variablesAnalysis, name);
-		this.cVariable = variablesAnalysis.createVariable(this.name, type, true, initValue);
+		this.cVariable = variablesAnalysis.createBottomVariable(this.name, type, true, initValue);
 	}
 
 	public CoreVariableAnalysis(@NonNull VariablesAnalysis variablesAnalysis, @NonNull String name, @NonNull Type type) {
diff --git a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtr2qvtc/RelationVariableAnalysis.java b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtr2qvtc/RelationVariableAnalysis.java
index 388cb954f..3aa562557 100644
--- a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtr2qvtc/RelationVariableAnalysis.java
+++ b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtr2qvtc/RelationVariableAnalysis.java
@@ -32,6 +32,7 @@ import org.eclipse.qvtd.pivot.qvtcore.CorePattern;
 import org.eclipse.qvtd.pivot.qvtcore.NavigationAssignment;
 import org.eclipse.qvtd.pivot.qvtcore.RealizedVariable;
 import org.eclipse.qvtd.pivot.qvtcore.VariableAssignment;
+import org.eclipse.qvtd.pivot.qvtcore.utilities.QVTcoreUtil;
 import org.eclipse.qvtd.pivot.qvtrelation.Key;
 import org.eclipse.qvtd.pivot.qvttemplate.ObjectTemplateExp;
 import org.eclipse.qvtd.pivot.qvttemplate.TemplateExp;
@@ -77,7 +78,7 @@ public class RelationVariableAnalysis extends AbstractVariableAnalysis
 			}
 		}
 		Variable cVariable2 = getCoreVariable();
-		List<@NonNull Assignment> cMiddleBottomAssignments = variablesAnalysis.getMiddleBottomPattern().getAssignment();
+		List<@NonNull Assignment> cMiddleBottomAssignments = QVTcoreUtil.getOwnedAssignments(variablesAnalysis.getMiddleBottomPattern());
 		if (!targetProperty.isIsMany() || (cExpression.getType() instanceof CollectionType)) {
 			VariableExp cSlotVariableExp = variablesAnalysis.createVariableExp(cVariable2);
 			NavigationAssignment cAssignment = variablesAnalysis.createNavigationAssignment(cSlotVariableExp, targetProperty, cExpression);
@@ -293,12 +294,12 @@ public class RelationVariableAnalysis extends AbstractVariableAnalysis
 			//
 			Type type = ClassUtil.nonNullState(rVariable.getType());
 			if (isKeyed) {
-				cVariable2 = variablesAnalysis.createVariable(name, type, true, null);
+				cVariable2 = variablesAnalysis.createBottomVariable(name, type, true, null);
 				initializeKeyedVariable(cVariable2);
 				cPattern.getVariable().add(cVariable2);
 			}
 			else if (!isRealized) {
-				cVariable2 = variablesAnalysis.createVariable(name, type, rVariable.isIsRequired(), null);
+				cVariable2 = variablesAnalysis.createBottomVariable(name, type, rVariable.isIsRequired(), null);
 				cPattern.getVariable().add(cVariable2);
 			}
 			else  {
diff --git a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtr2qvtc/VariablesAnalysis.java b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtr2qvtc/VariablesAnalysis.java
index 2125b39dd..5eb7f462e 100644
--- a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtr2qvtc/VariablesAnalysis.java
+++ b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtr2qvtc/VariablesAnalysis.java
@@ -335,7 +335,7 @@ import org.eclipse.qvtd.pivot.qvttemplate.TemplateExp;
 			OCLExpression cExpression = createVariableExp(cVariable);
 			NavigationAssignment cAssignment = createNavigationAssignment(cSlotVariableExp, cTargetProperty, cExpression);
 			QVTr2QVTc.SYNTHESIS.println("  addPropertyAssignment " + cAssignment);
-			assertNewAssignment(cMiddleBottomPattern.getAssignment(), cAssignment);
+			assertNewAssignment(QVTcoreUtil.getOwnedAssignments(cMiddleBottomPattern), cAssignment);
 			cMiddleBottomPattern.getAssignment().add(cAssignment);
 		}
 		return cVariable;
@@ -350,7 +350,7 @@ import org.eclipse.qvtd.pivot.qvttemplate.TemplateExp;
 		}
 	}
 
-	public void assertNewAssignment(@NonNull List<@NonNull Assignment> oldAssignments, @NonNull NavigationAssignment newAssignment) {
+	public void assertNewAssignment(@NonNull Iterable<@NonNull Assignment> oldAssignments, @NonNull NavigationAssignment newAssignment) {
 		//		if ("tr.action := sm".equals(newAssignment.toString())) {
 		//			newAssignment.toString();
 		//		}
@@ -358,7 +358,7 @@ import org.eclipse.qvtd.pivot.qvttemplate.TemplateExp;
 		if (newSlotExpression instanceof VariableExp) {
 			VariableDeclaration newVariable = ((VariableExp)newSlotExpression).getReferredVariable();
 			Property targetProperty = QVTcoreUtil.getTargetProperty(newAssignment);
-			for (Assignment oldAssignment : oldAssignments) {
+			for (@NonNull Assignment oldAssignment : oldAssignments) {
 				if (oldAssignment instanceof NavigationAssignment) {
 					if (QVTcoreUtil.getTargetProperty((NavigationAssignment)oldAssignment) == targetProperty) {
 						OCLExpression oldSlotExpression = ((NavigationAssignment)oldAssignment).getSlotExpression();
diff --git a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvts2qvti/BasicRegion2Mapping.java b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvts2qvti/BasicRegion2Mapping.java
index 9ffbbf851..689e4c0f1 100644
--- a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvts2qvti/BasicRegion2Mapping.java
+++ b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvts2qvti/BasicRegion2Mapping.java
@@ -222,6 +222,43 @@ public class BasicRegion2Mapping extends AbstractRegion2Mapping
 			return newTypedElements;
 		}
 
+		private @NonNull Variable createIteratorVariable(@NonNull Variable oldVariable) {
+			String name = oldVariable.getName();
+			assert name != null;
+			Type type = oldVariable.getType();
+			assert type != null;
+			assert oldVariable.getOwnedInit() == null;
+			Variable newVariable = helper.createIteratorVariable(name, type, oldVariable.isIsRequired());
+			Node variableNode = getNode(oldVariable);
+			if (variableNode != null) {
+				node2variable.put(variableNode, newVariable);
+			}
+			return newVariable;
+		}
+
+		private @NonNull List<@NonNull Variable> createIteratorVariables(@NonNull List<@NonNull Variable> oldVariables) {
+			List<@NonNull Variable> newVariables = new ArrayList<>(oldVariables.size());
+			for (@NonNull Variable oldVariable : oldVariables) {
+				Variable newVariable = createIteratorVariable(oldVariable);
+				newVariables.add(newVariable);
+			}
+			return newVariables;
+		}
+
+		private @NonNull Variable createLetVariable(@NonNull Variable oldVariable) {
+			String name = oldVariable.getName();
+			assert name != null;
+			Type type = oldVariable.getType();
+			assert type != null;
+			OCLExpression newInit = ClassUtil.nonNullState(create(oldVariable.getOwnedInit()));
+			Variable newVariable = helper.createLetVariable(name, type, oldVariable.isIsRequired(), newInit);
+			Node variableNode = getNode(oldVariable);
+			if (variableNode != null) {
+				node2variable.put(variableNode, newVariable);
+			}
+			return newVariable;
+		}
+
 		private @NonNull OCLExpression createNonNull(@Nullable OCLExpression oldTypedElement) {
 			assert oldTypedElement != null;
 			Node node = context.getNode(oldTypedElement);
@@ -231,16 +268,30 @@ public class BasicRegion2Mapping extends AbstractRegion2Mapping
 			return create(node);
 		}
 
-		private @NonNull List<@NonNull Variable> createVariables(@NonNull List<@NonNull Variable> oldVariables) {
+		private @NonNull Variable createResultVariable(@NonNull Variable oldVariable) {
+			String name = oldVariable.getName();
+			assert name != null;
+			Type type = oldVariable.getType();
+			assert type != null;
+			OCLExpression newInit = ClassUtil.nonNullState(create(oldVariable.getOwnedInit()));
+			Variable newVariable = helper.createResultVariable(name, type, oldVariable.isIsRequired(), newInit);
+			Node variableNode = getNode(oldVariable);
+			if (variableNode != null) {
+				node2variable.put(variableNode, newVariable);
+			}
+			return newVariable;
+		}
+
+		/*		private @NonNull List<@NonNull Variable> createVariables(@NonNull List<@NonNull Variable> oldVariables) {
 			List<@NonNull Variable> newVariables = new ArrayList<>(oldVariables.size());
 			for (@NonNull Variable oldVariable : oldVariables) {
 				Variable newVariable = createVariable(oldVariable);
 				newVariables.add(newVariable);
 			}
 			return newVariables;
-		}
+		} */
 
-		private @NonNull Variable createVariable(@NonNull Variable oldVariable) {
+		/*		private @NonNull Variable createVariable(@NonNull Variable oldVariable) {
 			String name = oldVariable.getName();
 			assert name != null;
 			Type type = oldVariable.getType();
@@ -251,7 +302,7 @@ public class BasicRegion2Mapping extends AbstractRegion2Mapping
 				node2variable.put(variableNode, newVariable);
 			}
 			return newVariable;
-		}
+		} */
 
 		public @Nullable OCLExpression getExpression(@NonNull Node node) {
 			if (node.isExplicitNull()) {
@@ -375,8 +426,8 @@ public class BasicRegion2Mapping extends AbstractRegion2Mapping
 		public @NonNull OCLExpression visitIterateExp(@NonNull IterateExp pIterateExp) {
 			OCLExpression iSource = create(pIterateExp.getOwnedSource());
 			assert iSource != null;
-			List<@NonNull ? extends Variable> iIterators = createVariables(ClassUtil.nullFree(pIterateExp.getOwnedIterators()));
-			Variable result = createVariable(ClassUtil.nonNull(pIterateExp.getOwnedResult()));
+			List<@NonNull ? extends Variable> iIterators = createIteratorVariables(ClassUtil.nullFree(pIterateExp.getOwnedIterators()));
+			Variable result = createResultVariable(ClassUtil.nonNull(pIterateExp.getOwnedResult()));
 			Iteration referredIteration = (Iteration) visitor.create(pIterateExp.getReferredIteration());
 			assert referredIteration != null;
 			OCLExpression iBody = getInlineExpressionCreator().create(pIterateExp.getOwnedBody());
@@ -388,7 +439,7 @@ public class BasicRegion2Mapping extends AbstractRegion2Mapping
 		public @NonNull OCLExpression visitIteratorExp(@NonNull IteratorExp pIteratorExp) {
 			OCLExpression iSource = create(pIteratorExp.getOwnedSource());
 			assert iSource != null;
-			List<@NonNull ? extends Variable> iIterators = createVariables(ClassUtil.nullFree(pIteratorExp.getOwnedIterators()));
+			List<@NonNull ? extends Variable> iIterators = createIteratorVariables(ClassUtil.nullFree(pIteratorExp.getOwnedIterators()));
 			Iteration referredIteration = (Iteration) visitor.create(pIteratorExp.getReferredIteration());
 			assert referredIteration != null;
 			OCLExpression iBody = getInlineExpressionCreator().create(pIteratorExp.getOwnedBody());
@@ -398,7 +449,7 @@ public class BasicRegion2Mapping extends AbstractRegion2Mapping
 
 		@Override
 		public @NonNull OCLExpression visitLetExp(@NonNull LetExp pLetExp) {
-			Variable asVariable = createVariable(ClassUtil.nonNull(pLetExp.getOwnedVariable()));
+			Variable asVariable = createLetVariable(ClassUtil.nonNull(pLetExp.getOwnedVariable()));
 			OCLExpression asInExpression = create(pLetExp.getOwnedIn());
 			assert asInExpression != null;
 			return helper.createLetExp(asVariable, asInExpression);
diff --git a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvts2qvti/RootRegion2Mapping.java b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvts2qvti/RootRegion2Mapping.java
index 08edbf696..3ca8ab69d 100644
--- a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvts2qvti/RootRegion2Mapping.java
+++ b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvts2qvti/RootRegion2Mapping.java
@@ -25,6 +25,7 @@ import org.eclipse.ocl.pivot.CollectionType;
 import org.eclipse.ocl.pivot.DataType;
 import org.eclipse.ocl.pivot.InvalidType;
 import org.eclipse.ocl.pivot.Iteration;
+import org.eclipse.ocl.pivot.IteratorVariable;
 import org.eclipse.ocl.pivot.OCLExpression;
 import org.eclipse.ocl.pivot.Operation;
 import org.eclipse.ocl.pivot.Property;
@@ -36,7 +37,6 @@ import org.eclipse.ocl.pivot.VoidType;
 import org.eclipse.ocl.pivot.ids.IdResolver;
 import org.eclipse.ocl.pivot.internal.complete.StandardLibraryInternal;
 import org.eclipse.ocl.pivot.utilities.NameUtil;
-import org.eclipse.ocl.pivot.utilities.PivotUtil;
 import org.eclipse.qvtd.compiler.internal.qvtp2qvts.Edge;
 import org.eclipse.qvtd.compiler.internal.qvtp2qvts.NavigableEdge;
 import org.eclipse.qvtd.compiler.internal.qvtp2qvts.Node;
@@ -264,7 +264,7 @@ public class RootRegion2Mapping extends AbstractScheduledRegion2Mapping
 		assert collectionType != null;
 		Type elementType = ((CollectionType)collectionType).getElementType();
 		assert elementType != null;
-		@NonNull Variable asIterator = PivotUtil.createVariable("i", elementType, true, null);
+		@NonNull IteratorVariable asIterator = helper.createIteratorVariable("i", elementType, true);
 		Property child2parentProperty = edge.getProperty().getOpposite();
 		assert child2parentProperty != null;
 		OCLExpression propertyCallExp = helper.createNavigationCallExp(helper.createVariableExp(asIterator), child2parentProperty);
diff --git a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtu2qvtm/QVTu2QVTm.java b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtu2qvtm/QVTu2QVTm.java
index edebc8bf5..f2199e936 100644
--- a/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtu2qvtm/QVTu2QVTm.java
+++ b/plugins/org.eclipse.qvtd.compiler/src/org/eclipse/qvtd/compiler/internal/qvtu2qvtm/QVTu2QVTm.java
@@ -23,7 +23,6 @@ import org.eclipse.jdt.annotation.Nullable;
 import org.eclipse.ocl.pivot.CompleteClass;
 import org.eclipse.ocl.pivot.Element;
 import org.eclipse.ocl.pivot.OCLExpression;
-import org.eclipse.ocl.pivot.PivotFactory;
 import org.eclipse.ocl.pivot.Property;
 import org.eclipse.ocl.pivot.Type;
 import org.eclipse.ocl.pivot.Variable;
@@ -31,6 +30,7 @@ import org.eclipse.ocl.pivot.VariableDeclaration;
 import org.eclipse.ocl.pivot.VariableExp;
 import org.eclipse.ocl.pivot.utilities.ClassUtil;
 import org.eclipse.ocl.pivot.utilities.EnvironmentFactory;
+import org.eclipse.ocl.pivot.utilities.PivotUtil;
 import org.eclipse.qvtd.compiler.internal.common.AbstractQVTc2QVTc;
 import org.eclipse.qvtd.compiler.internal.utilities.SymbolNameBuilder;
 import org.eclipse.qvtd.compiler.internal.utilities.SymbolNameReservation;
@@ -146,46 +146,46 @@ public class QVTu2QVTm extends AbstractQVTc2QVTc
 		protected boolean analyze() {
 			Area thisArea = getArea(getMapping());
 			if (thisArea != null) {
-				@SuppressWarnings("null")@NonNull GuardPattern thisGuardPattern = thisArea.getGuardPattern();
-				guardPredicates.addAll(ClassUtil.nullFree(thisGuardPattern.getPredicate()));
-				gatherVariables(thisGuardPattern.getVariable(), MergedVariable.GUARD);
-				@SuppressWarnings("null")@NonNull BottomPattern thisBottomPattern = thisArea.getBottomPattern();
-				gatherVariables(thisBottomPattern.getVariable(), MergedVariable.BOTTOM);
-				gatherAssignments(thisBottomPattern.getAssignment(), ASSIGNMENT);
-				bottomPredicates.addAll(ClassUtil.nullFree(thisBottomPattern.getPredicate()));
-				gatherVariables(thisBottomPattern.getRealizedVariable(), MergedVariable.BOTTOM);
+				GuardPattern thisGuardPattern = QVTcoreUtil.getGuardPattern(thisArea);
+				guardPredicates.addAll(QVTbaseUtil.getOwnedPredicates(thisGuardPattern));
+				gatherVariables(QVTcoreUtil.getOwnedVariables(thisGuardPattern), MergedVariable.GUARD);
+				BottomPattern thisBottomPattern = QVTcoreUtil.getBottomPattern(thisArea);
+				gatherVariables(QVTcoreUtil.getOwnedVariables(thisBottomPattern), MergedVariable.BOTTOM);
+				gatherAssignments(QVTcoreUtil.getOwnedAssignments(thisBottomPattern), ASSIGNMENT);
+				bottomPredicates.addAll(QVTbaseUtil.getOwnedPredicates(thisBottomPattern));
+				gatherVariables(QVTcoreUtil.getOwnedRealizedVariables(thisBottomPattern), MergedVariable.BOTTOM);
 			}
 			for (@NonNull Area childArea : getChildAreas()) {
-				@SuppressWarnings("null")@NonNull GuardPattern childGuardPattern = childArea.getGuardPattern();
-				guardPredicates.addAll(ClassUtil.nullFree(childGuardPattern.getPredicate()));
-				gatherVariables(childGuardPattern.getVariable(), MergedVariable.GUARD);
-				@SuppressWarnings("null")@NonNull BottomPattern childBottomPattern = childArea.getBottomPattern();
-				gatherVariables(childBottomPattern.getVariable(), MergedVariable.BOTTOM);
-				gatherAssignments(childBottomPattern.getAssignment(), ASSIGNMENT);
-				bottomPredicates.addAll(ClassUtil.nullFree(childBottomPattern.getPredicate()));
-				gatherVariables(childBottomPattern.getRealizedVariable(), MergedVariable.BOTTOM);
+				GuardPattern childGuardPattern = QVTcoreUtil.getGuardPattern(childArea);
+				guardPredicates.addAll(QVTbaseUtil.getOwnedPredicates(childGuardPattern));
+				gatherVariables(QVTcoreUtil.getOwnedVariables(childGuardPattern), MergedVariable.GUARD);
+				BottomPattern childBottomPattern = QVTcoreUtil.getBottomPattern(childArea);
+				gatherVariables(QVTcoreUtil.getOwnedVariables(childBottomPattern), MergedVariable.BOTTOM);
+				gatherAssignments(QVTcoreUtil.getOwnedAssignments(childBottomPattern), ASSIGNMENT);
+				bottomPredicates.addAll(QVTbaseUtil.getOwnedPredicates(childBottomPattern));
+				gatherVariables(QVTcoreUtil.getOwnedRealizedVariables(childBottomPattern), MergedVariable.BOTTOM);
 			}
 			for (@NonNull Area parentArea : getParentAreas()) {
 				assert (parentArea != thisArea);
-				@SuppressWarnings("null")@NonNull GuardPattern parentGuardPattern = parentArea.getGuardPattern();
-				guardPredicates.addAll(ClassUtil.nullFree(parentGuardPattern.getPredicate()));
-				gatherVariables(parentGuardPattern.getVariable(), MergedVariable.GUARD);
-				@SuppressWarnings("null")@NonNull BottomPattern parentBottomPattern = parentArea.getBottomPattern();
-				gatherVariables(parentBottomPattern.getVariable(), MergedVariable.GUARD);			// Hoist
-				gatherAssignments(parentBottomPattern.getAssignment(), PREDICATE);
-				guardPredicates.addAll(ClassUtil.nullFree(parentBottomPattern.getPredicate()));									// Hoist
-				gatherVariables(parentBottomPattern.getRealizedVariable(), MergedVariable.GUARD);	// Hoist
+				GuardPattern parentGuardPattern = QVTcoreUtil.getGuardPattern(parentArea);
+				guardPredicates.addAll(QVTbaseUtil.getOwnedPredicates(parentGuardPattern));
+				gatherVariables(QVTcoreUtil.getOwnedVariables(parentGuardPattern), MergedVariable.GUARD);
+				BottomPattern parentBottomPattern = QVTcoreUtil.getBottomPattern(parentArea);
+				gatherVariables(QVTcoreUtil.getOwnedVariables(parentBottomPattern), MergedVariable.GUARD);			// Hoist
+				gatherAssignments(QVTcoreUtil.getOwnedAssignments(parentBottomPattern), PREDICATE);
+				guardPredicates.addAll(QVTbaseUtil.getOwnedPredicates(parentBottomPattern));									// Hoist
+				gatherVariables(QVTcoreUtil.getOwnedRealizedVariables(parentBottomPattern), MergedVariable.GUARD);	// Hoist
 			}
 			for (@NonNull Area siblingArea : getSiblingAreas()) {
 				if (siblingArea != thisArea) {
-					@SuppressWarnings("null")@NonNull GuardPattern siblingGuardPattern = siblingArea.getGuardPattern();
-					guardPredicates.addAll(ClassUtil.nullFree(siblingGuardPattern.getPredicate()));
-					gatherVariables(siblingGuardPattern.getVariable(), MergedVariable.GUARD);
-					@SuppressWarnings("null")@NonNull BottomPattern siblingBottomPattern = siblingArea.getBottomPattern();
-					gatherVariables(siblingBottomPattern.getVariable(), MergedVariable.BOTTOM);		// FIXME legacy compatibility
-					gatherAssignments(siblingBottomPattern.getAssignment(), ASSIGNMENT);
-					bottomPredicates.addAll(ClassUtil.nullFree(siblingBottomPattern.getPredicate()));		// FIXME legacy compatibility
-					gatherVariables(siblingBottomPattern.getRealizedVariable(), MergedVariable.BOTTOM);
+					GuardPattern siblingGuardPattern = QVTcoreUtil.getGuardPattern(siblingArea);
+					guardPredicates.addAll(QVTbaseUtil.getOwnedPredicates(siblingGuardPattern));
+					gatherVariables(QVTcoreUtil.getOwnedVariables(siblingGuardPattern), MergedVariable.GUARD);
+					BottomPattern siblingBottomPattern = QVTcoreUtil.getBottomPattern(siblingArea);
+					gatherVariables(QVTcoreUtil.getOwnedVariables(siblingBottomPattern), MergedVariable.BOTTOM);		// FIXME legacy compatibility
+					gatherAssignments(QVTcoreUtil.getOwnedAssignments(siblingBottomPattern), ASSIGNMENT);
+					bottomPredicates.addAll(QVTbaseUtil.getOwnedPredicates(siblingBottomPattern));		// FIXME legacy compatibility
+					gatherVariables(QVTcoreUtil.getOwnedRealizedVariables(siblingBottomPattern), MergedVariable.BOTTOM);
 				}
 			}
 			return true;
@@ -300,7 +300,7 @@ public class QVTu2QVTm extends AbstractQVTc2QVTc
 			BottomPattern mBottomPattern = QVTcoreFactory.eINSTANCE.createBottomPattern();
 			mArea.setBottomPattern(mBottomPattern);
 			createVisitor.createAll(bottomPredicates, mBottomPattern.getPredicate());
-			synthesizeNavigationAssignments(mBottomPattern.getAssignment());
+			synthesizeNavigationAssignments(QVTcoreUtil.getOwnedAssignments(mBottomPattern));
 			if (variableName2mergedVariables != null) {
 				for (@NonNull MergedVariable mergedVariable : variableName2mergedVariables.values()) {		// FIXME Change to alphabetical sort
 					mergedVariable.synthesize(mArea);
@@ -314,11 +314,11 @@ public class QVTu2QVTm extends AbstractQVTc2QVTc
 					createVisitor.createAll(uArea.getOwnedComments(), mArea.getOwnedComments());
 				}
 				//
-				@SuppressWarnings("null")@NonNull GuardPattern uGuardPattern = uArea.getGuardPattern();
+				GuardPattern uGuardPattern = QVTcoreUtil.getGuardPattern(uArea);
 				qvtu2qvtm.addTrace(uGuardPattern, mGuardPattern);
 				createVisitor.createAll(uGuardPattern.getOwnedComments(), mGuardPattern.getOwnedComments());
 				//
-				@SuppressWarnings("null")@NonNull BottomPattern uBottomPattern = uArea.getBottomPattern();
+				BottomPattern uBottomPattern = QVTcoreUtil.getBottomPattern(uArea);
 				qvtu2qvtm.addTrace(uBottomPattern, mBottomPattern);
 				createVisitor.createAll(uBottomPattern.getOwnedComments(), mArea.getOwnedComments());
 			}
@@ -695,11 +695,12 @@ public class QVTu2QVTm extends AbstractQVTc2QVTc
 					mArea.getBottomPattern().getRealizedVariable().add(realizedVariable);
 				}
 				else {
-					mVariable = PivotFactory.eINSTANCE.createVariable();
 					if (isGuard) {
+						mVariable = QVTcoreFactory.eINSTANCE.createGuardVariable();
 						mArea.getGuardPattern().getVariable().add(mVariable);
 					}
 					else {
+						mVariable = QVTcoreFactory.eINSTANCE.createBottomVariable();
 						mArea.getBottomPattern().getVariable().add(mVariable);
 					}
 				}
@@ -731,9 +732,9 @@ public class QVTu2QVTm extends AbstractQVTc2QVTc
 				assert assignments2 != null;
 				VariableAssignment mVariableAssignment = createVisitor.create(assignments2.get(0));
 				assert mVariableAssignment != null;
-				for (@NonNull VariableAssignment uVariableAssignment : assignments2) {
-					//					createVisitor.getContext().addTrace(uVariableAssignment, mVariableAssignment);
-				}
+				//				for (@NonNull VariableAssignment uVariableAssignment : assignments2) {
+				//					createVisitor.getContext().addTrace(uVariableAssignment, mVariableAssignment);
+				//				}
 			}
 		}
 
@@ -838,14 +839,14 @@ public class QVTu2QVTm extends AbstractQVTc2QVTc
 			while (uNamedMapping.getContext() != null) {
 				uNamedMapping = uNamedMapping.getContext();
 			}
-			s.appendString(String.valueOf(uNamedMapping.getName()));
+			s.appendString(PivotUtil.getName(uNamedMapping));
 			List<@NonNull String> guardVariableNames = new ArrayList<@NonNull String>();
 			for (@NonNull Variable guardVariable : ClassUtil.nullFree(uMapping.getGuardPattern().getVariable())) {
-				guardVariableNames.add(String.valueOf(guardVariable.getName()));
+				guardVariableNames.add(PivotUtil.getName(guardVariable));
 			}
 			for (@NonNull Domain uDomain : ClassUtil.nullFree(uMapping.getDomain())) {
 				for (@NonNull Variable guardVariable : ClassUtil.nullFree(((CoreDomain)uDomain).getGuardPattern().getVariable())) {
-					guardVariableNames.add(String.valueOf(guardVariable.getName()));
+					guardVariableNames.add(PivotUtil.getName(guardVariable));
 				}
 			}
 			Collections.sort(guardVariableNames);
diff --git a/plugins/org.eclipse.qvtd.cs2as.compiler/src/org/eclipse/qvtd/cs2as/compiler/internal/OCL2QVTp.java b/plugins/org.eclipse.qvtd.cs2as.compiler/src/org/eclipse/qvtd/cs2as/compiler/internal/OCL2QVTp.java
index f58b02d5c..8dabd0747 100644
--- a/plugins/org.eclipse.qvtd.cs2as.compiler/src/org/eclipse/qvtd/cs2as/compiler/internal/OCL2QVTp.java
+++ b/plugins/org.eclipse.qvtd.cs2as.compiler/src/org/eclipse/qvtd/cs2as/compiler/internal/OCL2QVTp.java
@@ -23,11 +23,9 @@ import static org.eclipse.qvtd.cs2as.compiler.internal.OCL2QVTpUtil.getUpdateMap
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
-import java.util.Map;
 import java.util.Set;
 import java.util.function.Function;
 import java.util.function.Predicate;
-import java.util.logging.Logger;
 import java.util.stream.Collectors;
 
 import org.eclipse.emf.common.util.URI;
@@ -36,7 +34,6 @@ import org.eclipse.emf.ecore.resource.Resource;
 import org.eclipse.emf.ecore.resource.ResourceSet;
 import org.eclipse.emf.ecore.util.EcoreUtil;
 import org.eclipse.jdt.annotation.NonNull;
-import org.eclipse.jdt.annotation.Nullable;
 import org.eclipse.ocl.pivot.Class;
 import org.eclipse.ocl.pivot.ExpressionInOCL;
 import org.eclipse.ocl.pivot.IfExp;
@@ -74,10 +71,10 @@ import org.eclipse.qvtd.pivot.qvtcore.RealizedVariable;
 
 public class OCL2QVTp {
 
-	private @NonNull Logger logger = Logger.getLogger(getClass().getName());
+	//	private @NonNull Logger logger = Logger.getLogger(getClass().getName());
 	private @NonNull EnvironmentFactory envFact;
 	private @NonNull String traceabilityPropName;
-	private @Nullable Map<?,?> saveOptions;
+	//	private @Nullable Map<?,?> saveOptions;
 
 	public static final @NonNull String RIGHT_MODEL_TYPE_NAME = "rightAS";
 	public static final @NonNull String LEFT_MODEL_TYPE_NAME = "leftCS";
@@ -356,7 +353,7 @@ public class OCL2QVTp {
 		domain.setTypedModel(leftTypedModel);
 		domain.setIsCheckable(true);
 
-		Variable variable = PivotFactory.eINSTANCE.createVariable();
+		Variable variable = QVTcoreFactory.eINSTANCE.createGuardVariable();
 		variable.setName("l"+firstToUpperCase().apply(type.getName()));
 		variable.setType(type);
 
diff --git a/plugins/org.eclipse.qvtd.pivot.qvtbase/src/org/eclipse/qvtd/pivot/qvtbase/utilities/QVTbaseUtil.java b/plugins/org.eclipse.qvtd.pivot.qvtbase/src/org/eclipse/qvtd/pivot/qvtbase/utilities/QVTbaseUtil.java
index c36e0ac01..c11746717 100644
--- a/plugins/org.eclipse.qvtd.pivot.qvtbase/src/org/eclipse/qvtd/pivot/qvtbase/utilities/QVTbaseUtil.java
+++ b/plugins/org.eclipse.qvtd.pivot.qvtbase/src/org/eclipse/qvtd/pivot/qvtbase/utilities/QVTbaseUtil.java
@@ -189,7 +189,7 @@ public class QVTbaseUtil extends PivotUtil
 			//        	if (transformationType == null) {	// FIXME BUG 487123
 			//        		throw new IllegalLibraryException("No Transformation type in standard library.");		// FIXME need to be using a derived EnvironmentFactory
 			//        	}
-			ownedContext = PivotFactory.eINSTANCE.createVariable();
+			ownedContext = PivotFactory.eINSTANCE.createParameterVariable();
 			ownedContext.setName("this");
 			ownedContext.setType(transformation);		// FIXME promote API
 			//           	ownedContext.setTypeValue(transformation);
@@ -208,7 +208,7 @@ public class QVTbaseUtil extends PivotUtil
 	public static @NonNull Variable getContextVariable(@NonNull StandardLibraryInternal standardLibrary, @NonNull TypedModel typedModel) {
 		Variable ownedContext = typedModel.getOwnedContext();
 		if (ownedContext == null) {
-			ownedContext = PivotFactory.eINSTANCE.createVariable();
+			ownedContext = PivotFactory.eINSTANCE.createParameterVariable();
 			ownedContext.setName(typedModel.getName());
 			ownedContext.setType(standardLibrary.getLibraryType("Model"));
 			//        	ownedContext.setTypeValue(typedModel);
diff --git a/plugins/org.eclipse.qvtd.pivot.qvtcore/src/org/eclipse/qvtd/pivot/qvtcore/utilities/QVTcoreHelper.java b/plugins/org.eclipse.qvtd.pivot.qvtcore/src/org/eclipse/qvtd/pivot/qvtcore/utilities/QVTcoreHelper.java
index 777cb8965..b43b9d10c 100644
--- a/plugins/org.eclipse.qvtd.pivot.qvtcore/src/org/eclipse/qvtd/pivot/qvtcore/utilities/QVTcoreHelper.java
+++ b/plugins/org.eclipse.qvtd.pivot.qvtcore/src/org/eclipse/qvtd/pivot/qvtcore/utilities/QVTcoreHelper.java
@@ -10,31 +10,18 @@
  *******************************************************************************/
 package org.eclipse.qvtd.pivot.qvtcore.utilities;
 
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-
-import org.eclipse.emf.common.util.TreeIterator;
-import org.eclipse.emf.ecore.EObject;
-import org.eclipse.emf.ecore.EReference;
 import org.eclipse.jdt.annotation.NonNull;
 import org.eclipse.jdt.annotation.Nullable;
-import org.eclipse.ocl.pivot.CallExp;
-import org.eclipse.ocl.pivot.CollectionType;
-import org.eclipse.ocl.pivot.Element;
-import org.eclipse.ocl.pivot.LetExp;
 import org.eclipse.ocl.pivot.OCLExpression;
-import org.eclipse.ocl.pivot.Operation;
 import org.eclipse.ocl.pivot.Property;
 import org.eclipse.ocl.pivot.Type;
 import org.eclipse.ocl.pivot.Variable;
-import org.eclipse.ocl.pivot.internal.manager.PivotMetamodelManager;
-import org.eclipse.ocl.pivot.internal.utilities.PivotUtilInternal;
 import org.eclipse.ocl.pivot.utilities.EnvironmentFactory;
-import org.eclipse.ocl.pivot.utilities.NameUtil;
 import org.eclipse.qvtd.pivot.qvtbase.utilities.QVTbaseHelper;
 import org.eclipse.qvtd.pivot.qvtcore.BottomPattern;
+import org.eclipse.qvtd.pivot.qvtcore.BottomVariable;
 import org.eclipse.qvtd.pivot.qvtcore.GuardPattern;
+import org.eclipse.qvtd.pivot.qvtcore.GuardVariable;
 import org.eclipse.qvtd.pivot.qvtcore.Mapping;
 import org.eclipse.qvtd.pivot.qvtcore.NavigationAssignment;
 import org.eclipse.qvtd.pivot.qvtcore.OppositePropertyAssignment;
@@ -52,6 +39,23 @@ public class QVTcoreHelper extends QVTbaseHelper
 		super(environmentFactory);
 	}
 
+	public @NonNull BottomVariable createBottomVariable(@NonNull String name, @NonNull Type asType, boolean isRequired, @Nullable OCLExpression asInitExpression) {
+		BottomVariable asVariable = QVTcoreFactory.eINSTANCE.createBottomVariable();
+		asVariable.setName(name);
+		asVariable.setType(asType);
+		asVariable.setIsRequired(isRequired);
+		asVariable.setOwnedInit(asInitExpression);
+		return asVariable;
+	}
+
+	public @NonNull GuardVariable createGuardVariable(@NonNull String name, @NonNull Type asType, boolean isRequired) {
+		GuardVariable asVariable = QVTcoreFactory.eINSTANCE.createGuardVariable();
+		asVariable.setName(name);
+		asVariable.setType(asType);
+		asVariable.setIsRequired(isRequired);
+		return asVariable;
+	}
+
 	public @NonNull Mapping createMapping(@Nullable String name) {
 		Mapping coreMapping = QVTcoreFactory.eINSTANCE.createMapping();
 		coreMapping.setName(name);
@@ -93,94 +97,4 @@ public class QVTcoreHelper extends QVTbaseHelper
 		asVariableAssignment.setValue(asValueExpression);
 		return asVariableAssignment;
 	}
-
-	/**
-	 * Rewrite asTree and all its descendants to replace all "?." and "?->" navigations by their safe counterparts.
-	 * @deprecated-promote to PivotHelper for M4.
-	 */
-	@Deprecated
-	public void rewriteSafeNavigations(@NonNull Element asTree) {
-		//
-		//	Locate all unsafe calls first to avoid CME from concurrent locate/rewrite.
-		//
-		List<@NonNull CallExp> unsafeCallExps = null;
-		if (asTree instanceof CallExp) {
-			unsafeCallExps = rewriteUnsafeCallExp_Gather(unsafeCallExps, (CallExp)asTree);
-		}
-		for (TreeIterator<EObject> tit = asTree.eAllContents(); tit.hasNext(); ) {
-			EObject eObject = tit.next();
-			if (eObject instanceof CallExp) {
-				unsafeCallExps = rewriteUnsafeCallExp_Gather(unsafeCallExps, (CallExp)eObject);
-			}
-		}
-		//
-		//	Rewrite the unsafe calls
-		//
-		if (unsafeCallExps != null) {
-			PivotMetamodelManager metamodelManager = (PivotMetamodelManager) environmentFactory.getMetamodelManager();
-			org.eclipse.ocl.pivot.Class oclAnyType = environmentFactory.getStandardLibrary().getOclAnyType();
-			Operation oclEqualsOperation = NameUtil.getNameable(oclAnyType.getOwnedOperations(), "=");
-			assert oclEqualsOperation != null;
-			org.eclipse.ocl.pivot.Class collectionType = environmentFactory.getStandardLibrary().getCollectionType();
-			Operation excludingOperation = NameUtil.getNameable(collectionType.getOwnedOperations(), "excluding");
-			assert excludingOperation != null;
-			for (CallExp unsafeCallExp : unsafeCallExps) {
-				OCLExpression source = unsafeCallExp.getOwnedSource();
-				assert source != null;
-				if (source.getType() instanceof CollectionType) {
-					rewriteUnsafeCollectionCallExp(metamodelManager, excludingOperation, unsafeCallExp);
-				}
-				else {
-					rewriteUnsafeObjectCallExp(metamodelManager, oclEqualsOperation, unsafeCallExp);
-				}
-			}
-		}
-	}
-
-	private @Nullable List<@NonNull CallExp> rewriteUnsafeCallExp_Gather(@Nullable List<@NonNull CallExp> unsafeCallExps, @NonNull CallExp callExp) {
-		OCLExpression source = callExp.getOwnedSource();
-		if ((source != null) && callExp.isIsSafe()) {
-			if (unsafeCallExps == null) {
-				unsafeCallExps = new ArrayList<@NonNull CallExp>();
-			}
-			unsafeCallExps.add(callExp);
-		}
-		return unsafeCallExps;
-	}
-
-	private void rewriteUnsafeCollectionCallExp(@NonNull PivotMetamodelManager metamodelManager, @NonNull Operation excludingOperation, @NonNull CallExp unsafeCollectionCallExp) {
-		unsafeCollectionCallExp.setIsSafe(false);
-		EObject eContainer = unsafeCollectionCallExp.eContainer();
-		EReference eContainmentFeature = unsafeCollectionCallExp.eContainmentFeature();
-		PivotUtilInternal.resetContainer(unsafeCollectionCallExp);
-		//
-		OCLExpression nullExpression = metamodelManager.createNullLiteralExp();
-		OCLExpression safeCollectionCallExp = createOperationCallExp(unsafeCollectionCallExp, excludingOperation, Collections.singletonList(nullExpression));
-		//
-		eContainer.eSet(eContainmentFeature, safeCollectionCallExp);
-	}
-
-	private  void rewriteUnsafeObjectCallExp(@NonNull PivotMetamodelManager metamodelManager, @NonNull Operation oclEqualsOperation, @NonNull CallExp unsafeObjectCallExp) {
-		unsafeObjectCallExp.setIsSafe(false);
-		EObject eContainer = unsafeObjectCallExp.eContainer();
-		EReference eContainmentFeature = unsafeObjectCallExp.eContainmentFeature();
-		PivotUtilInternal.resetContainer(unsafeObjectCallExp);
-		OCLExpression oldSourceExpression = unsafeObjectCallExp.getOwnedSource();
-		assert oldSourceExpression != null;
-		//
-		Variable unsafeSourceVariable = createVariable("unsafe", oldSourceExpression);
-		OCLExpression unsafeSourceExpression1 = createVariableExp(unsafeSourceVariable);
-		unsafeObjectCallExp.setOwnedSource(unsafeSourceExpression1);
-		//
-		OCLExpression unsafeSourceExpression2 = createVariableExp(unsafeSourceVariable);
-		OCLExpression nullExpression = metamodelManager.createNullLiteralExp();
-		OCLExpression isUnsafeExpression = createOperationCallExp(unsafeSourceExpression2, oclEqualsOperation, Collections.singletonList(nullExpression));
-		//
-		OCLExpression thenExpression = metamodelManager.createNullLiteralExp();
-		OCLExpression safeObjectCallExp = metamodelManager.createIfExp(isUnsafeExpression, thenExpression, unsafeObjectCallExp);
-		//
-		LetExp safeExp = createLetExp(unsafeSourceVariable, safeObjectCallExp);
-		//
-		eContainer.eSet(eContainmentFeature, safeExp);
-	}
 }
\ No newline at end of file
diff --git a/plugins/org.eclipse.qvtd.pivot.qvtcore/src/org/eclipse/qvtd/pivot/qvtcore/utilities/QVTcorePrettyPrintVisitor.java b/plugins/org.eclipse.qvtd.pivot.qvtcore/src/org/eclipse/qvtd/pivot/qvtcore/utilities/QVTcorePrettyPrintVisitor.java
index 9c55c9790..57c232e18 100644
--- a/plugins/org.eclipse.qvtd.pivot.qvtcore/src/org/eclipse/qvtd/pivot/qvtcore/utilities/QVTcorePrettyPrintVisitor.java
+++ b/plugins/org.eclipse.qvtd.pivot.qvtcore/src/org/eclipse/qvtd/pivot/qvtcore/utilities/QVTcorePrettyPrintVisitor.java
@@ -21,11 +21,13 @@ import org.eclipse.qvtd.pivot.qvtbase.utilities.QVTbasePrettyPrintVisitor;
 import org.eclipse.qvtd.pivot.qvtcore.Area;
 import org.eclipse.qvtd.pivot.qvtcore.Assignment;
 import org.eclipse.qvtd.pivot.qvtcore.BottomPattern;
+import org.eclipse.qvtd.pivot.qvtcore.BottomVariable;
 import org.eclipse.qvtd.pivot.qvtcore.CoreDomain;
 import org.eclipse.qvtd.pivot.qvtcore.CoreModel;
 import org.eclipse.qvtd.pivot.qvtcore.CorePattern;
 import org.eclipse.qvtd.pivot.qvtcore.EnforcementOperation;
 import org.eclipse.qvtd.pivot.qvtcore.GuardPattern;
+import org.eclipse.qvtd.pivot.qvtcore.GuardVariable;
 import org.eclipse.qvtd.pivot.qvtcore.Mapping;
 import org.eclipse.qvtd.pivot.qvtcore.NavigationAssignment;
 import org.eclipse.qvtd.pivot.qvtcore.OppositePropertyAssignment;
@@ -80,6 +82,11 @@ public class QVTcorePrettyPrintVisitor extends QVTbasePrettyPrintVisitor impleme
 	}
 
 	@Override
+	public Object visitBottomVariable(@NonNull BottomVariable object) {
+		return visitVariable(object);
+	}
+
+	@Override
 	public Object visitCoreDomain(@NonNull CoreDomain object) {
 		// TODO Auto-generated method stub
 		return null;
@@ -120,6 +127,11 @@ public class QVTcorePrettyPrintVisitor extends QVTbasePrettyPrintVisitor impleme
 	}
 
 	@Override
+	public Object visitGuardVariable(@NonNull GuardVariable object) {
+		return visitVariable(object);
+	}
+
+	@Override
 	public Object visitMapping(@NonNull Mapping pMapping) {
 		context.append("map ");
 		context.appendName(pMapping);
diff --git a/plugins/org.eclipse.qvtd.pivot.qvtcore/src/org/eclipse/qvtd/pivot/qvtcore/utilities/QVTcoreToStringVisitor.java b/plugins/org.eclipse.qvtd.pivot.qvtcore/src/org/eclipse/qvtd/pivot/qvtcore/utilities/QVTcoreToStringVisitor.java
index 47c1a2cc4..4fab8fe58 100644
--- a/plugins/org.eclipse.qvtd.pivot.qvtcore/src/org/eclipse/qvtd/pivot/qvtcore/utilities/QVTcoreToStringVisitor.java
+++ b/plugins/org.eclipse.qvtd.pivot.qvtcore/src/org/eclipse/qvtd/pivot/qvtcore/utilities/QVTcoreToStringVisitor.java
@@ -17,11 +17,13 @@ import org.eclipse.ocl.pivot.utilities.ToStringVisitor;
 import org.eclipse.qvtd.pivot.qvtbase.utilities.QVTbaseToStringVisitor;
 import org.eclipse.qvtd.pivot.qvtcore.Assignment;
 import org.eclipse.qvtd.pivot.qvtcore.BottomPattern;
+import org.eclipse.qvtd.pivot.qvtcore.BottomVariable;
 import org.eclipse.qvtd.pivot.qvtcore.CoreDomain;
 import org.eclipse.qvtd.pivot.qvtcore.CoreModel;
 import org.eclipse.qvtd.pivot.qvtcore.CorePattern;
 import org.eclipse.qvtd.pivot.qvtcore.EnforcementOperation;
 import org.eclipse.qvtd.pivot.qvtcore.GuardPattern;
+import org.eclipse.qvtd.pivot.qvtcore.GuardVariable;
 import org.eclipse.qvtd.pivot.qvtcore.Mapping;
 import org.eclipse.qvtd.pivot.qvtcore.NavigationAssignment;
 import org.eclipse.qvtd.pivot.qvtcore.OppositePropertyAssignment;
@@ -78,6 +80,11 @@ public class QVTcoreToStringVisitor extends QVTbaseToStringVisitor implements QV
 	}
 
 	@Override
+	public String visitBottomVariable(@NonNull BottomVariable object) {
+		return visitVariable(object);
+	}
+
+	@Override
 	public String visitCoreDomain(@NonNull CoreDomain object) {
 		appendQualifiedName(object);
 		return null;
@@ -110,6 +117,11 @@ public class QVTcoreToStringVisitor extends QVTbaseToStringVisitor implements QV
 	}
 
 	@Override
+	public String visitGuardVariable(@NonNull GuardVariable object) {
+		return visitVariable(object);
+	}
+
+	@Override
 	public String visitMapping(@NonNull Mapping object) {
 		append("mapping ");
 		appendName(object);
diff --git a/plugins/org.eclipse.qvtd.pivot.qvtcore/src/org/eclipse/qvtd/pivot/qvtcore/utilities/QVTcoreUtil.java b/plugins/org.eclipse.qvtd.pivot.qvtcore/src/org/eclipse/qvtd/pivot/qvtcore/utilities/QVTcoreUtil.java
index cebc6a695..868e62942 100644
--- a/plugins/org.eclipse.qvtd.pivot.qvtcore/src/org/eclipse/qvtd/pivot/qvtcore/utilities/QVTcoreUtil.java
+++ b/plugins/org.eclipse.qvtd.pivot.qvtcore/src/org/eclipse/qvtd/pivot/qvtcore/utilities/QVTcoreUtil.java
@@ -39,13 +39,17 @@ import org.eclipse.qvtd.pivot.qvtbase.utilities.QVTbaseEnvironmentFactory;
 import org.eclipse.qvtd.pivot.qvtbase.utilities.QVTbaseEnvironmentFactory.CreateStrategy;
 import org.eclipse.qvtd.pivot.qvtbase.utilities.QVTbaseUtil;
 import org.eclipse.qvtd.pivot.qvtcore.Area;
+import org.eclipse.qvtd.pivot.qvtcore.Assignment;
+import org.eclipse.qvtd.pivot.qvtcore.BottomPattern;
 import org.eclipse.qvtd.pivot.qvtcore.CoreDomain;
 import org.eclipse.qvtd.pivot.qvtcore.CoreModel;
 import org.eclipse.qvtd.pivot.qvtcore.CorePattern;
+import org.eclipse.qvtd.pivot.qvtcore.GuardPattern;
 import org.eclipse.qvtd.pivot.qvtcore.Mapping;
 import org.eclipse.qvtd.pivot.qvtcore.NavigationAssignment;
 import org.eclipse.qvtd.pivot.qvtcore.OppositePropertyAssignment;
 import org.eclipse.qvtd.pivot.qvtcore.PropertyAssignment;
+import org.eclipse.qvtd.pivot.qvtcore.RealizedVariable;
 
 public class QVTcoreUtil extends QVTbaseUtil
 {
@@ -94,6 +98,10 @@ public class QVTcoreUtil extends QVTbaseUtil
 		return mapping;
 	}
 
+	public static @NonNull BottomPattern getBottomPattern(@NonNull Area area) {
+		return ClassUtil.nonNullState(area.getBottomPattern());
+	}
+
 	public static @Nullable Area getContainingArea(@Nullable EObject eObject) {
 		for ( ; eObject != null; eObject = eObject.eContainer()) {
 			if (eObject instanceof Area) {
@@ -125,6 +133,22 @@ public class QVTcoreUtil extends QVTbaseUtil
 		return (CoreDomain)getDomain((Rule)rule, typedModel);
 	}
 
+	public static @NonNull GuardPattern getGuardPattern(@NonNull Area area) {
+		return ClassUtil.nonNullState(area.getGuardPattern());
+	}
+
+	public static @NonNull List<@NonNull Assignment> getOwnedAssignments(@NonNull BottomPattern bottomPattern) {
+		return ClassUtil.nullFree(bottomPattern.getAssignment());
+	}
+
+	public static @NonNull List<@NonNull RealizedVariable> getOwnedRealizedVariables(@NonNull BottomPattern bottomPattern) {
+		return ClassUtil.nullFree(bottomPattern.getRealizedVariable());
+	}
+
+	public static @NonNull List<@NonNull Variable> getOwnedVariables(@NonNull CorePattern corePattern) {
+		return ClassUtil.nullFree(corePattern.getVariable());
+	}
+
 	public static @NonNull Property getTargetProperty(@NonNull NavigationAssignment asNavigationAssignment) {
 		if (asNavigationAssignment instanceof PropertyAssignment) {
 			return ClassUtil.nonNullState(((PropertyAssignment)asNavigationAssignment).getTargetProperty());
diff --git a/plugins/org.eclipse.qvtd.pivot.qvtrelation/src/org/eclipse/qvtd/pivot/qvtrelation/utilities/QVTrelationHelper.java b/plugins/org.eclipse.qvtd.pivot.qvtrelation/src/org/eclipse/qvtd/pivot/qvtrelation/utilities/QVTrelationHelper.java
index 7f8d9f54f..dda5fa42d 100644
--- a/plugins/org.eclipse.qvtd.pivot.qvtrelation/src/org/eclipse/qvtd/pivot/qvtrelation/utilities/QVTrelationHelper.java
+++ b/plugins/org.eclipse.qvtd.pivot.qvtrelation/src/org/eclipse/qvtd/pivot/qvtrelation/utilities/QVTrelationHelper.java
@@ -11,8 +11,13 @@
 package org.eclipse.qvtd.pivot.qvtrelation.utilities;
 
 import org.eclipse.jdt.annotation.NonNull;
+import org.eclipse.jdt.annotation.Nullable;
+import org.eclipse.ocl.pivot.OCLExpression;
+import org.eclipse.ocl.pivot.Type;
 import org.eclipse.ocl.pivot.utilities.EnvironmentFactory;
 import org.eclipse.qvtd.pivot.qvtbase.utilities.QVTbaseHelper;
+import org.eclipse.qvtd.pivot.qvtrelation.QVTrelationFactory;
+import org.eclipse.qvtd.pivot.qvtrelation.SharedVariable;
 
 /**
  * QVTrelationHelper provides helper routines to assist creation of QVTrelation model elements.
@@ -22,4 +27,13 @@ public class QVTrelationHelper extends QVTbaseHelper
 	public QVTrelationHelper(@NonNull EnvironmentFactory environmentFactory) {
 		super(environmentFactory);
 	}
+
+	public @NonNull SharedVariable createSharedVariable(@NonNull String name, @NonNull Type asType, boolean isRequired, @Nullable OCLExpression asInitExpression) {
+		SharedVariable asVariable = QVTrelationFactory.eINSTANCE.createSharedVariable();
+		asVariable.setName(name);
+		asVariable.setType(asType);
+		asVariable.setIsRequired(isRequired);
+		asVariable.setOwnedInit(asInitExpression);
+		return asVariable;
+	}
 }
\ No newline at end of file
diff --git a/plugins/org.eclipse.qvtd.pivot.qvtrelation/src/org/eclipse/qvtd/pivot/qvtrelation/utilities/QVTrelationPrettyPrintVisitor.java b/plugins/org.eclipse.qvtd.pivot.qvtrelation/src/org/eclipse/qvtd/pivot/qvtrelation/utilities/QVTrelationPrettyPrintVisitor.java
index 88f92e9b5..ca05f557c 100644
--- a/plugins/org.eclipse.qvtd.pivot.qvtrelation/src/org/eclipse/qvtd/pivot/qvtrelation/utilities/QVTrelationPrettyPrintVisitor.java
+++ b/plugins/org.eclipse.qvtd.pivot.qvtrelation/src/org/eclipse/qvtd/pivot/qvtrelation/utilities/QVTrelationPrettyPrintVisitor.java
@@ -24,6 +24,8 @@ import org.eclipse.qvtd.pivot.qvtrelation.RelationDomainAssignment;
 import org.eclipse.qvtd.pivot.qvtrelation.RelationImplementation;
 import org.eclipse.qvtd.pivot.qvtrelation.RelationModel;
 import org.eclipse.qvtd.pivot.qvtrelation.RelationalTransformation;
+import org.eclipse.qvtd.pivot.qvtrelation.SharedVariable;
+import org.eclipse.qvtd.pivot.qvtrelation.TemplateVariable;
 import org.eclipse.qvtd.pivot.qvtrelation.util.QVTrelationVisitor;
 import org.eclipse.qvtd.pivot.qvttemplate.ObjectTemplateExp;
 import org.eclipse.qvtd.pivot.qvttemplate.TemplateExp;
@@ -109,10 +111,20 @@ public class QVTrelationPrettyPrintVisitor extends QVTtemplatePrettyPrintVisitor
 	}
 
 	@Override
+	public Object visitSharedVariable(@NonNull SharedVariable object) {
+		return visitVariable(object);
+	}
+
+	@Override
 	public Object visitTemplateExp(@NonNull TemplateExp object) {
 		context.appendName(object);
 		context.append(" : ");
 		context.appendTypedMultiplicity(object);
 		return null;
 	}
+
+	@Override
+	public Object visitTemplateVariable(@NonNull TemplateVariable object) {
+		return visitVariable(object);
+	}
 }
diff --git a/plugins/org.eclipse.qvtd.pivot.qvtrelation/src/org/eclipse/qvtd/pivot/qvtrelation/utilities/QVTrelationToStringVisitor.java b/plugins/org.eclipse.qvtd.pivot.qvtrelation/src/org/eclipse/qvtd/pivot/qvtrelation/utilities/QVTrelationToStringVisitor.java
index 8530db7b2..795723d42 100644
--- a/plugins/org.eclipse.qvtd.pivot.qvtrelation/src/org/eclipse/qvtd/pivot/qvtrelation/utilities/QVTrelationToStringVisitor.java
+++ b/plugins/org.eclipse.qvtd.pivot.qvtrelation/src/org/eclipse/qvtd/pivot/qvtrelation/utilities/QVTrelationToStringVisitor.java
@@ -27,6 +27,8 @@ import org.eclipse.qvtd.pivot.qvtrelation.RelationDomainAssignment;
 import org.eclipse.qvtd.pivot.qvtrelation.RelationImplementation;
 import org.eclipse.qvtd.pivot.qvtrelation.RelationModel;
 import org.eclipse.qvtd.pivot.qvtrelation.RelationalTransformation;
+import org.eclipse.qvtd.pivot.qvtrelation.SharedVariable;
+import org.eclipse.qvtd.pivot.qvtrelation.TemplateVariable;
 import org.eclipse.qvtd.pivot.qvtrelation.util.QVTrelationVisitor;
 import org.eclipse.qvtd.pivot.qvttemplate.utilities.QVTtemplateToStringVisitor;
 
@@ -130,7 +132,7 @@ public class QVTrelationToStringVisitor extends QVTtemplateToStringVisitor imple
 		}
 		append("domain ");
 		appendName(object);
-/*		append(" ");
+		/*		append(" ");
 		boolean isFirst = true;
 		for (DomainPattern pattern : object.getPattern()) {
 			if (!isFirst) {
@@ -176,4 +178,14 @@ public class QVTrelationToStringVisitor extends QVTtemplateToStringVisitor imple
 		append(")");
 		return null;
 	}
+
+	@Override
+	public String visitSharedVariable(@NonNull SharedVariable object) {
+		return visitVariable(object);
+	}
+
+	@Override
+	public String visitTemplateVariable(@NonNull TemplateVariable object) {
+		return visitVariable(object);
+	}
 }
diff --git a/plugins/org.eclipse.qvtd.xtext.qvtcore/src/org/eclipse/qvtd/xtext/qvtcore/as2cs/QVTcoreDeclarationVisitor.java b/plugins/org.eclipse.qvtd.xtext.qvtcore/src/org/eclipse/qvtd/xtext/qvtcore/as2cs/QVTcoreDeclarationVisitor.java
index b595ac3b7..27deec27a 100644
--- a/plugins/org.eclipse.qvtd.xtext.qvtcore/src/org/eclipse/qvtd/xtext/qvtcore/as2cs/QVTcoreDeclarationVisitor.java
+++ b/plugins/org.eclipse.qvtd.xtext.qvtcore/src/org/eclipse/qvtd/xtext/qvtcore/as2cs/QVTcoreDeclarationVisitor.java
@@ -62,11 +62,13 @@ import org.eclipse.qvtd.pivot.qvtbase.Transformation;
 import org.eclipse.qvtd.pivot.qvtbase.TypedModel;
 import org.eclipse.qvtd.pivot.qvtcore.Assignment;
 import org.eclipse.qvtd.pivot.qvtcore.BottomPattern;
+import org.eclipse.qvtd.pivot.qvtcore.BottomVariable;
 import org.eclipse.qvtd.pivot.qvtcore.CoreDomain;
 import org.eclipse.qvtd.pivot.qvtcore.CoreModel;
 import org.eclipse.qvtd.pivot.qvtcore.CorePattern;
 import org.eclipse.qvtd.pivot.qvtcore.EnforcementOperation;
 import org.eclipse.qvtd.pivot.qvtcore.GuardPattern;
+import org.eclipse.qvtd.pivot.qvtcore.GuardVariable;
 import org.eclipse.qvtd.pivot.qvtcore.Mapping;
 import org.eclipse.qvtd.pivot.qvtcore.NavigationAssignment;
 import org.eclipse.qvtd.pivot.qvtcore.OppositePropertyAssignment;
@@ -332,6 +334,11 @@ public class QVTcoreDeclarationVisitor extends QVTbaseDeclarationVisitor impleme
 	}
 
 	@Override
+	public ElementCS visitBottomVariable(@NonNull BottomVariable object) {
+		return visitVariable(object);
+	}
+
+	@Override
 	public ElementCS visitCoreDomain(@NonNull CoreDomain asCoreDomain) {
 		DomainCS csDomain = createCoreDomain(asCoreDomain);
 		csDomain.setPivot(asCoreDomain);
@@ -431,6 +438,11 @@ public class QVTcoreDeclarationVisitor extends QVTbaseDeclarationVisitor impleme
 	}
 
 	@Override
+	public ElementCS visitGuardVariable(@NonNull GuardVariable object) {
+		return visitVariable(object);
+	}
+
+	@Override
 	public ElementCS visitMapping(@NonNull Mapping asMapping) {
 		String defaultName = asMapping.getContext() != null ? null : "«null»";
 		MappingCS csMapping = context.refreshNamedElement(MappingCS.class, QVTcoreCSPackage.Literals.MAPPING_CS, asMapping, defaultName);
diff --git a/plugins/org.eclipse.qvtd.xtext.qvtcore/src/org/eclipse/qvtd/xtext/qvtcore/cs2as/QVTcoreCSContainmentVisitor.java b/plugins/org.eclipse.qvtd.xtext.qvtcore/src/org/eclipse/qvtd/xtext/qvtcore/cs2as/QVTcoreCSContainmentVisitor.java
index c8244ff56..3f5b45a30 100644
--- a/plugins/org.eclipse.qvtd.xtext.qvtcore/src/org/eclipse/qvtd/xtext/qvtcore/cs2as/QVTcoreCSContainmentVisitor.java
+++ b/plugins/org.eclipse.qvtd.xtext.qvtcore/src/org/eclipse/qvtd/xtext/qvtcore/cs2as/QVTcoreCSContainmentVisitor.java
@@ -45,10 +45,12 @@ import org.eclipse.qvtd.pivot.qvtbase.TypedModel;
 import org.eclipse.qvtd.pivot.qvtbase.utilities.QVTbaseUtil;
 import org.eclipse.qvtd.pivot.qvtcore.Assignment;
 import org.eclipse.qvtd.pivot.qvtcore.BottomPattern;
+import org.eclipse.qvtd.pivot.qvtcore.BottomVariable;
 import org.eclipse.qvtd.pivot.qvtcore.CoreDomain;
 import org.eclipse.qvtd.pivot.qvtcore.CoreModel;
 import org.eclipse.qvtd.pivot.qvtcore.EnforcementOperation;
 import org.eclipse.qvtd.pivot.qvtcore.GuardPattern;
+import org.eclipse.qvtd.pivot.qvtcore.GuardVariable;
 import org.eclipse.qvtd.pivot.qvtcore.Mapping;
 import org.eclipse.qvtd.pivot.qvtcore.PropertyAssignment;
 import org.eclipse.qvtd.pivot.qvtcore.QVTcoreFactory;
@@ -369,7 +371,12 @@ public class QVTcoreCSContainmentVisitor extends AbstractQVTcoreCSContainmentVis
 
 	@Override
 	public Continuation<?> visitUnrealizedVariableCS(@NonNull UnrealizedVariableCS csElement) {
-		refreshNamedElement(Variable.class, PivotPackage.Literals.VARIABLE, csElement);
+		if (csElement.eContainer() instanceof GuardPatternCS) {
+			refreshNamedElement(GuardVariable.class, QVTcorePackage.Literals.GUARD_VARIABLE, csElement);
+		}
+		else {
+			refreshNamedElement(BottomVariable.class, QVTcorePackage.Literals.BOTTOM_VARIABLE, csElement);
+		}
 		return null;
 	}
 }
diff --git a/plugins/org.eclipse.qvtd.xtext.qvtimperative/src/org/eclipse/qvtd/xtext/qvtimperative/cs2as/QVTimperativeCSContainmentVisitor.java b/plugins/org.eclipse.qvtd.xtext.qvtimperative/src/org/eclipse/qvtd/xtext/qvtimperative/cs2as/QVTimperativeCSContainmentVisitor.java
index d9d48394d..275bfed4c 100644
--- a/plugins/org.eclipse.qvtd.xtext.qvtimperative/src/org/eclipse/qvtd/xtext/qvtimperative/cs2as/QVTimperativeCSContainmentVisitor.java
+++ b/plugins/org.eclipse.qvtd.xtext.qvtimperative/src/org/eclipse/qvtd/xtext/qvtimperative/cs2as/QVTimperativeCSContainmentVisitor.java
@@ -32,6 +32,7 @@ import org.eclipse.ocl.xtext.base.cs2as.Continuation;
 import org.eclipse.ocl.xtext.base.cs2as.SingleContinuation;
 import org.eclipse.ocl.xtext.base.utilities.BaseCSResource;
 import org.eclipse.ocl.xtext.basecs.PathNameCS;
+import org.eclipse.ocl.xtext.essentialoclcs.VariableCS;
 import org.eclipse.qvtd.pivot.qvtbase.Function;
 import org.eclipse.qvtd.pivot.qvtbase.FunctionParameter;
 import org.eclipse.qvtd.pivot.qvtbase.QVTbasePackage;
@@ -396,4 +397,10 @@ public class QVTimperativeCSContainmentVisitor extends AbstractQVTimperativeCSCo
 		QVTbaseUtil.getContextVariable(standardLibrary, asTransformation);
 		return null;
 	}
+
+	@Override
+	public Continuation<?> visitVariableCS(@NonNull VariableCS csElement) {
+		refreshNamedElement(LoopVariable.class, QVTimperativePackage.Literals.LOOP_VARIABLE, csElement);
+		return null;
+	}
 }
diff --git a/plugins/org.eclipse.qvtd.xtext.qvtrelation/src/org/eclipse/qvtd/xtext/qvtrelation/cs2as/QVTrelationCSContainmentVisitor.java b/plugins/org.eclipse.qvtd.xtext.qvtrelation/src/org/eclipse/qvtd/xtext/qvtrelation/cs2as/QVTrelationCSContainmentVisitor.java
index 000658a6a..a4030d41e 100644
--- a/plugins/org.eclipse.qvtd.xtext.qvtrelation/src/org/eclipse/qvtd/xtext/qvtrelation/cs2as/QVTrelationCSContainmentVisitor.java
+++ b/plugins/org.eclipse.qvtd.xtext.qvtrelation/src/org/eclipse/qvtd/xtext/qvtrelation/cs2as/QVTrelationCSContainmentVisitor.java
@@ -23,7 +23,6 @@ import org.eclipse.ocl.pivot.Model;
 import org.eclipse.ocl.pivot.Namespace;
 import org.eclipse.ocl.pivot.OCLExpression;
 import org.eclipse.ocl.pivot.Operation;
-import org.eclipse.ocl.pivot.PivotFactory;
 import org.eclipse.ocl.pivot.PivotPackage;
 import org.eclipse.ocl.pivot.Property;
 import org.eclipse.ocl.pivot.Variable;
@@ -51,12 +50,15 @@ import org.eclipse.qvtd.pivot.qvtbase.TypedModel;
 import org.eclipse.qvtd.pivot.qvtbase.utilities.QVTbaseUtil;
 import org.eclipse.qvtd.pivot.qvtrelation.DomainPattern;
 import org.eclipse.qvtd.pivot.qvtrelation.Key;
+import org.eclipse.qvtd.pivot.qvtrelation.QVTrelationFactory;
 import org.eclipse.qvtd.pivot.qvtrelation.QVTrelationPackage;
 import org.eclipse.qvtd.pivot.qvtrelation.Relation;
 import org.eclipse.qvtd.pivot.qvtrelation.RelationDomain;
 import org.eclipse.qvtd.pivot.qvtrelation.RelationDomainAssignment;
 import org.eclipse.qvtd.pivot.qvtrelation.RelationModel;
 import org.eclipse.qvtd.pivot.qvtrelation.RelationalTransformation;
+import org.eclipse.qvtd.pivot.qvtrelation.SharedVariable;
+import org.eclipse.qvtd.pivot.qvtrelation.TemplateVariable;
 import org.eclipse.qvtd.pivot.qvtrelation.utilities.QVTrelationUtil;
 import org.eclipse.qvtd.pivot.qvttemplate.CollectionTemplateExp;
 import org.eclipse.qvtd.pivot.qvttemplate.ObjectTemplateExp;
@@ -117,7 +119,7 @@ public class QVTrelationCSContainmentVisitor extends AbstractQVTrelationCSContai
 			if (pKey != null) {
 				pKey.setIdentifies(csElement.getClassId());
 				PivotUtilInternal.refreshList(pKey.getPart(), csElement.getPropertyIds());
-				List<Property> oppositePart = new ArrayList<Property>();
+				List<Property> oppositePart = new ArrayList<>();
 				for (PathNameCS oppositePropertyId : csElement.getOwnedOppositePropertyIds()) {
 					Element element = oppositePropertyId.getReferredElement();
 					if (element instanceof Property) {
@@ -140,7 +142,7 @@ public class QVTrelationCSContainmentVisitor extends AbstractQVTrelationCSContai
 		public BasicContinuation<?> execute() {
 			TypedModel pTypedModel = PivotUtil.getPivot(TypedModel.class, csElement);
 			if (pTypedModel != null) {
-				List<org.eclipse.ocl.pivot.Package> newUsedPackage = new ArrayList<org.eclipse.ocl.pivot.Package>();
+				List<org.eclipse.ocl.pivot.Package> newUsedPackage = new ArrayList<>();
 				for (Namespace metamodelId : csElement.getMetamodelIds()) {
 					if (metamodelId instanceof Model) {
 						newUsedPackage.addAll(((Model)metamodelId).getOwnedPackages());
@@ -235,7 +237,7 @@ public class QVTrelationCSContainmentVisitor extends AbstractQVTrelationCSContai
 					String name = getElementTemplateName((ElementTemplateCS) csMember);
 					VariableExp asVariableExp = context.refreshModelElement(VariableExp.class, PivotPackage.Literals.VARIABLE_EXP, csMember);
 					if (name == null) {
-						Variable asMemberVariable = PivotFactory.eINSTANCE.createVariable();
+						Variable asMemberVariable = QVTrelationFactory.eINSTANCE.createSharedVariable();
 						asMemberVariable.setName(QVTrelationUtil.DUMMY_VARIABLE_NAME + specialVariables.size());
 						asMemberVariable.setIsImplicit(true);
 						specialVariables.add(asMemberVariable);
@@ -261,7 +263,7 @@ public class QVTrelationCSContainmentVisitor extends AbstractQVTrelationCSContai
 					}
 				}
 				else {
-					asRestVariable = context.refreshModelElement(Variable.class, PivotPackage.Literals.VARIABLE, csRestTemplate);
+					asRestVariable = context.refreshModelElement(SharedVariable.class, QVTrelationPackage.Literals.SHARED_VARIABLE, csRestTemplate);
 					asRestVariable.setIsImplicit(true);
 					asRestVariable.setTypeValue(null);
 					asRestVariable.setIsRequired(true);
@@ -278,7 +280,7 @@ public class QVTrelationCSContainmentVisitor extends AbstractQVTrelationCSContai
 	protected void resolveTemplateVariable(@NonNull TemplateCS csElement, @NonNull TemplateExp pivotElement) {
 		Variable variable = pivotElement.getBindsTo();
 		if (variable == null) {
-			variable = ClassUtil.nonNullEMF(PivotFactory.eINSTANCE.createVariable());
+			variable = QVTrelationFactory.eINSTANCE.createTemplateVariable();
 			pivotElement.setBindsTo(variable);
 		}
 		context.refreshName(variable, csElement.getName());
@@ -309,10 +311,10 @@ public class QVTrelationCSContainmentVisitor extends AbstractQVTrelationCSContai
 		context.refreshPivotList(DomainPattern.class, asPatterns, csElement.getOwnedPattern());
 		context.refreshPivotList(RelationDomainAssignment.class, pivotElement.getDefaultAssignment(), csElement.getOwnedDefaultValues());
 		if (asPatterns.size() > 0) {
-			List<Variable> rootVariables = new ArrayList<Variable>();
+			List<Variable> rootVariables = new ArrayList<>();
 			for (DomainPattern asPattern : asPatterns) {
 				if (asPattern != null) {
-					//					List<@NonNull Variable> boundVariables = new ArrayList<@NonNull Variable>();
+					//					List<@NonNull Variable> boundVariables = new ArrayList<>();
 					TemplateExp asTemplate = asPattern.getTemplateExpression();
 					if (asTemplate != null) {
 						rootVariables.add(asTemplate.getBindsTo());
@@ -395,18 +397,18 @@ public class QVTrelationCSContainmentVisitor extends AbstractQVTrelationCSContai
 	public Continuation<?> visitPrimitiveTypeDomainCS(@NonNull PrimitiveTypeDomainCS csElement) {
 		@NonNull RelationDomain pivotElement = context.refreshModelElement(RelationDomain.class, QVTrelationPackage.Literals.RELATION_DOMAIN, csElement);
 		@NonNull DomainPattern asPattern = context.refreshModelElement(DomainPattern.class, QVTrelationPackage.Literals.DOMAIN_PATTERN, null);
-		List<DomainPattern> asPatterns = new ArrayList<DomainPattern>();
+		List<DomainPattern> asPatterns = new ArrayList<>();
 		asPatterns.add(asPattern);
 		PivotUtilInternal.refreshList(pivotElement.getPattern(), asPatterns);
 		@NonNull TemplateExp template = context.refreshModelElement(TemplateExp.class, QVTtemplatePackage.Literals.OBJECT_TEMPLATE_EXP, null);
 		asPattern.setTemplateExpression(template);
-		@NonNull Variable rootVariable = context.refreshModelElement(Variable.class, PivotPackage.Literals.VARIABLE, null);
+		@NonNull TemplateVariable rootVariable = context.refreshModelElement(TemplateVariable.class, QVTrelationPackage.Literals.TEMPLATE_VARIABLE, null);
 		context.refreshName(rootVariable, csElement.getName());
 		template.setBindsTo(rootVariable);
-		List<Variable> rootVariables = new ArrayList<Variable>();
+		List<Variable> rootVariables = new ArrayList<>();
 		rootVariables.add(rootVariable);
 		PivotUtilInternal.refreshList(pivotElement.getRootVariable(), rootVariables);
-		List<Variable> pivotVariables = new ArrayList<Variable>();
+		List<Variable> pivotVariables = new ArrayList<>();
 		pivotVariables.add(rootVariable);
 		PivotUtilInternal.refreshList(asPattern.getBindsTo(), pivotVariables);
 		return null;
@@ -463,7 +465,7 @@ public class QVTrelationCSContainmentVisitor extends AbstractQVTrelationCSContai
 				domain.setIsEnforceable(isEnforceable);
 			}
 		}
-		List<@NonNull Variable> relationVariables = new ArrayList<@NonNull Variable>();
+		List<@NonNull Variable> relationVariables = new ArrayList<>();
 		//
 		//	Gather explicit local variables.
 		//
@@ -487,12 +489,12 @@ public class QVTrelationCSContainmentVisitor extends AbstractQVTrelationCSContai
 		//
 		//	Resolve the special variables.
 		//
-		List<@NonNull Variable> specialVariables = new ArrayList<@NonNull Variable>();
+		List<@NonNull Variable> specialVariables = new ArrayList<>();
 		for (@NonNull AbstractDomainCS csAbstractDomain : ClassUtil.nullFree(csElement.getOwnedDomains())) {
 			if (csAbstractDomain instanceof DomainCS) {
 				for (@NonNull DomainPatternCS csDomainPatternCS : ClassUtil.nullFree(((DomainCS)csAbstractDomain).getOwnedPattern())) {
 					DomainPattern asPattern = PivotUtil.getPivot(DomainPattern.class, csDomainPatternCS);
-					List<@NonNull Variable> boundVariables = new ArrayList<@NonNull Variable>();
+					List<@NonNull Variable> boundVariables = new ArrayList<>();
 					TemplateCS csTemplate = csDomainPatternCS.getOwnedTemplate();
 					if (csTemplate != null) {
 						processSpecialVariables(relationVariables, boundVariables, specialVariables, csTemplate);
@@ -569,7 +571,7 @@ public class QVTrelationCSContainmentVisitor extends AbstractQVTrelationCSContai
 	@Override
 	public Continuation<?> visitVarDeclarationIdCS(@NonNull VarDeclarationIdCS csElement) {
 		@SuppressWarnings("unused")
-		Variable pivotElement = refreshNamedElement(Variable.class, PivotPackage.Literals.VARIABLE, csElement);
+		SharedVariable pivotElement = refreshNamedElement(SharedVariable.class, QVTrelationPackage.Literals.SHARED_VARIABLE, csElement);
 		return null;
 	}
 }
diff --git a/plugins/org.eclipse.qvtd.xtext.qvtrelation/src/org/eclipse/qvtd/xtext/qvtrelation/scoping/QVTrelationPathElementCSAttribution.java b/plugins/org.eclipse.qvtd.xtext.qvtrelation/src/org/eclipse/qvtd/xtext/qvtrelation/scoping/QVTrelationPathElementCSAttribution.java
index 35baf8bb9..a3fdde940 100644
--- a/plugins/org.eclipse.qvtd.xtext.qvtrelation/src/org/eclipse/qvtd/xtext/qvtrelation/scoping/QVTrelationPathElementCSAttribution.java
+++ b/plugins/org.eclipse.qvtd.xtext.qvtrelation/src/org/eclipse/qvtd/xtext/qvtrelation/scoping/QVTrelationPathElementCSAttribution.java
@@ -21,6 +21,7 @@ import org.eclipse.ocl.pivot.internal.scoping.ScopeView;
 import org.eclipse.ocl.pivot.utilities.PivotUtil;
 import org.eclipse.ocl.xtext.base.attributes.PathElementCSAttribution;
 import org.eclipse.qvtd.pivot.qvtrelation.Relation;
+import org.eclipse.qvtd.pivot.qvtrelation.utilities.QVTrelationHelper;
 import org.eclipse.qvtd.pivot.qvtrelation.utilities.QVTrelationUtil;
 import org.eclipse.qvtd.xtext.qvtrelationcs.RelationCS;
 
@@ -36,10 +37,11 @@ public class QVTrelationPathElementCSAttribution extends PathElementCSAttributio
 				if (eObject instanceof RelationCS) {
 					Relation relation = PivotUtil.getPivot(Relation.class, (RelationCS)eObject);
 					if (relation != null) {
+						QVTrelationHelper helper = new QVTrelationHelper(environmentView.getEnvironmentFactory());
 						List<Variable> variables = relation.getVariable();
 						AnyType oclAnyType = environmentView.getStandardLibrary().getOclAnyType();
 						String variableName = QVTrelationUtil.DUMMY_VARIABLE_NAME + variables.size();
-						Variable asVariable = PivotUtil.createVariable(variableName, oclAnyType, true, null);
+						Variable asVariable = helper.createSharedVariable(variableName, oclAnyType, true, null);
 						asVariable.setIsImplicit(true);
 						variables.add(asVariable);
 						environmentView.addElement(QVTrelationUtil.DUMMY_VARIABLE_NAME, asVariable);
@@ -49,9 +51,9 @@ public class QVTrelationPathElementCSAttribution extends PathElementCSAttributio
 			}
 			return null;
 		}
-//		else if (name == null) {
-//			env
-//		}
+		//		else if (name == null) {
+		//			env
+		//		}
 		return super.computeLookup(target, environmentView, scopeView);
 	}
 }