diff --git a/AlgebraicDataflowArchitectureModel/src/algorithms/TypeInference.java b/AlgebraicDataflowArchitectureModel/src/algorithms/TypeInference.java
index 1be6a1d..45a82b9 100644
--- a/AlgebraicDataflowArchitectureModel/src/algorithms/TypeInference.java
+++ b/AlgebraicDataflowArchitectureModel/src/algorithms/TypeInference.java
@@ -379,7 +379,7 @@
 				}
 				for (Term t : terms) {
 					Symbol symbol = t.getSymbol();
-					if (symbol.equals(DataConstraintModel.cons) || symbol.equals(DataConstraintModel.set)) {
+					if (symbol.equals(DataConstraintModel.cons) || symbol.equals(DataConstraintModel.set) || symbol.equals(DataConstraintModel.append)) {
 						// If the root symbol of the term is cons or set.
 						List<Expression> consExps = new ArrayList<>();
 						consExps.add(t);	// list term
@@ -390,10 +390,18 @@
 								consExps.add(e);
 								updateExpressionBelonging(expToConsOrSet, e, consExps);
 							}
+						} else if (symbol.equals(DataConstraintModel.append)) {
+							// If the root symbol of the term is append.
+							Expression e = t.getChildren().get(1);
+							consExps.add(e);	// list element
+							updateExpressionBelonging(expToConsOrSet, e, consExps);
+							e = t.getChildren().get(0);
+							consExps.add(e);	// list argument
+							updateExpressionBelonging(expToConsOrSet, e, consExps);							
 						} else {
 							// If the root symbol of the term is set.
 							Expression e = t.getChildren().get(2);
-							consExps.add(e);	// list component
+							consExps.add(e);	// list element
 							updateExpressionBelonging(expToConsOrSet, e, consExps);
 							e = t.getChildren().get(0);
 							consExps.add(e);	// list argument
@@ -401,7 +409,7 @@
 						}
 						Type newType = getExpTypeIfUpdatable(t.getType(), consExps.get(2));
 						if (newType != null) {
-							// If the type of the 2nd argument of cons (1st argument of set) is more concrete than the type of the term.
+							// If the type of the 2nd argument of cons (1st argument of set/append) is more concrete than the type of the term.
 							t.setType(newType);
 							Map<Integer, Expression> updateCons = getUpdateSet(updateFromConsOrSet, consExps);
 							updateCons.put(System.identityHashCode(t), t);
@@ -410,7 +418,7 @@
 							if (consExps.get(2) != null && consExps.get(2) instanceof Variable) {
 								arg2Type = ((Variable) consExps.get(2)).getType();
 								if (compareTypes(arg2Type, t.getType())) {
-									// If the type of the term is more concrete than the type of the 2nd argument of cons (1st argument of set).
+									// If the type of the term is more concrete than the type of the 2nd argument of cons (1st argument of set/append).
 									((Variable) consExps.get(2)).setType(t.getType());
 									Map<Integer, Expression> updateCons = getUpdateSet(updateFromConsOrSet, consExps);
 									updateCons.put(System.identityHashCode(consExps.get(2)), consExps.get(2));
@@ -418,7 +426,7 @@
 							} else if (consExps.get(2) != null && consExps.get(2) instanceof Term) {
 								arg2Type = ((Term) consExps.get(2)).getType();
 								if (compareTypes(arg2Type, t.getType())) {
-									// If the type of the term is more concrete than the type of the 2nd argument of cons (1st argument of set).
+									// If the type of the term is more concrete than the type of the 2nd argument of cons (1st argument of set/append).
 									((Term) consExps.get(2)).setType(t.getType());
 									Map<Integer, Expression> updateCons = getUpdateSet(updateFromConsOrSet, consExps);
 									updateCons.put(System.identityHashCode(consExps.get(2)), consExps.get(2));
@@ -815,6 +823,33 @@
 						} else {
 							newCompTypeList.add(null);
 						}
+						Type newTermType = getExpTypeIfUpdatable(termType, mapExps.get(3));
+						if (newTermType != null) {
+							// If the type of the 1st argument of insert is more concrete than the type of the term.
+							t.setType(newTermType);
+							termType = newTermType;
+							Map<Integer, Expression> updateExps = getUpdateSet(updateFromMap, mapExps);
+							updateExps.put(System.identityHashCode(t), t);
+						} else {
+							Type arg3Type = null;
+							if (mapExps.get(3) != null && mapExps.get(3) instanceof Variable) {
+								arg3Type = ((Variable) mapExps.get(3)).getType();
+								if (compareTypes(arg3Type, t.getType())) {
+									// If the type of the term is more concrete than the type of the 1st argument of insert.
+									((Variable) mapExps.get(3)).setType(t.getType());
+									Map<Integer, Expression> updateExps = getUpdateSet(updateFromMap, mapExps);
+									updateExps.put(System.identityHashCode(mapExps.get(3)), mapExps.get(3));
+								}
+							} else if (mapExps.get(3) != null && mapExps.get(3) instanceof Term) {
+								arg3Type = ((Term) mapExps.get(3)).getType();
+								if (compareTypes(arg3Type, t.getType())) {
+									// If the type of the term is more concrete than the type of the 1st argument of insert.
+									((Term) mapExps.get(3)).setType(t.getType());
+									Map<Integer, Expression> updateExps = getUpdateSet(updateFromMap, mapExps);
+									updateExps.put(System.identityHashCode(mapExps.get(3)), mapExps.get(3));
+								}
+							}
+						}
 						if (termType == DataConstraintModel.typeMap || termType == null) {
 							Type newMapType = mapTypes.get(newCompTypeList);
 							if (newMapType == null) {
@@ -823,9 +858,16 @@
 							}
 							// Update the type of the map term and record the updated expression.
 							t.setType(newMapType);
-							termType = newMapType;
 							Map<Integer, Expression> updateExps = getUpdateSet(updateFromMap, mapExps);
 							updateExps.put(System.identityHashCode(t), t);
+							if (mapExps.get(3) != null && mapExps.get(3) instanceof Variable) {
+								((Variable) mapExps.get(3)).setType(newMapType);
+								updateExps.put(System.identityHashCode(mapExps.get(3)), mapExps.get(3));
+							} else if (mapExps.get(3) != null && mapExps.get(3) instanceof Term) {
+								((Term) mapExps.get(3)).setType(newMapType);
+								updateExps.put(System.identityHashCode(mapExps.get(3)), mapExps.get(3));
+							}
+							termType = newMapType;
 						}
 						map.put(System.identityHashCode(mapExps), termType);
 					} else if (symbol.equals(DataConstraintModel.addMember)) {
diff --git a/AlgebraicDataflowArchitectureModel/src/application/actions/SaveAsAction.java b/AlgebraicDataflowArchitectureModel/src/application/actions/SaveAsAction.java
index 1a38b08..9542cdb 100644
--- a/AlgebraicDataflowArchitectureModel/src/application/actions/SaveAsAction.java
+++ b/AlgebraicDataflowArchitectureModel/src/application/actions/SaveAsAction.java
@@ -65,9 +65,7 @@
 				lastDir = fc.getSelectedFile().getParent();
 				
 				String fileName = fc.getSelectedFile().getAbsolutePath() + extension;
-				
-				// checking file duplicates
-				if(! (fc.getSelectedFile().exists()))  editor.setCurFilePath(fileName);	
+				editor.setCurFilePath(fileName);	
 				
 				// overwriting file
 				editor.save();
diff --git a/AlgebraicDataflowArchitectureModel/src/application/editor/Editor.java b/AlgebraicDataflowArchitectureModel/src/application/editor/Editor.java
index 66107cf..b0db12f 100644
--- a/AlgebraicDataflowArchitectureModel/src/application/editor/Editor.java
+++ b/AlgebraicDataflowArchitectureModel/src/application/editor/Editor.java
@@ -235,15 +235,11 @@
             return;
         }
         File file = new File(curFilePath);
-        if (!file.exists()) {
-            return;
-        }
         // get a file's extension
         String extension = file.getName().substring(file.getName().lastIndexOf("."));
         if (extension.contains(".model")) {
             saveModel(file);
-        }
-        if (extension.contains(".dtram")) {
+        } else if (extension.contains(".dtram")) {
             saveDTRAM(file);
         }
     }
diff --git a/AlgebraicDataflowArchitectureModel/src/generators/CodeGeneratorFromDataFlowGraph.java b/AlgebraicDataflowArchitectureModel/src/generators/CodeGeneratorFromDataFlowGraph.java
index 14182ed..1fd7a65 100644
--- a/AlgebraicDataflowArchitectureModel/src/generators/CodeGeneratorFromDataFlowGraph.java
+++ b/AlgebraicDataflowArchitectureModel/src/generators/CodeGeneratorFromDataFlowGraph.java
@@ -237,46 +237,60 @@
 		return params;
 	}
 	
-	private void addUpdateStatementWithConstructorInvocationToMethod(MethodDeclaration method, Expression exp, ResourceHierarchy childRes, TypeDeclaration childComponent, ILanguageSpecific langSpec) {
-		Type replacedJsonType = childRes.getResourceStateType();
-		String replacingClassName = getComponentName(childRes, langSpec);
+	private void addUpdateStatementWithConstructorInvocationToMethod(MethodDeclaration method, Expression exp, ResourceHierarchy descendantRes, TypeDeclaration descendantComponent, ILanguageSpecific langSpec) {
+		Type replacedJsonType = descendantRes.getResourceStateType();
+		String replacingClassName = getComponentName(descendantRes, langSpec);
+		Type descendantType = new Type(replacingClassName, replacingClassName);
 		Map<Position, Term> subTerms = ((Term) exp).getSubTerms(Term.class);
 		Iterator<Entry<Position, Term>> termEntItr = subTerms.entrySet().iterator();
 		while (termEntItr.hasNext()) {
 			Entry<Position, Term> termEnt = termEntItr.next();
 			Term jsonTerm = termEnt.getValue();
-			if (jsonTerm.getType() != null && jsonTerm.getType().equals(replacedJsonType)) {
-				if (jsonTerm instanceof JsonTerm || jsonTerm.getSymbol().equals(DataConstraintModel.addMember)) {
-					MethodDeclaration childConstructor = getConstructor(childComponent);
-					List<String> params = new ArrayList<>();
-					for (VariableDeclaration var: childConstructor.getParameters()) {
-						JsonAccessor jsonMember = new JsonAccessor(DataConstraintModel.dot);
-						jsonMember.addChild(jsonTerm);
-						jsonMember.addChild(new Constant(var.getName(), DataConstraintModel.typeString));
-						Expression param = jsonMember.reduce();
-						if (param != null) {
-							if (param instanceof Term) {
-								if (((Term) param).getType() == null) {
-									((Term) param).setType(var.getType());
+			if (jsonTerm.getType() != null) {
+				if (jsonTerm.getType().equals(replacedJsonType)) {
+					if (jsonTerm instanceof JsonTerm || jsonTerm.getSymbol().equals(DataConstraintModel.addMember)) {
+						MethodDeclaration childConstructor = getConstructor(descendantComponent);
+						List<String> params = new ArrayList<>();
+						for (VariableDeclaration var: childConstructor.getParameters()) {
+							JsonAccessor jsonMember = new JsonAccessor(DataConstraintModel.dot);
+							jsonMember.addChild(jsonTerm);
+							jsonMember.addChild(new Constant(var.getName(), DataConstraintModel.typeString));
+							Expression param = jsonMember.reduce();
+							if (param != null) {
+								if (param instanceof Term) {
+									if (((Term) param).getType() == null) {
+										((Term) param).setType(var.getType());
+									}
+								} else if (param instanceof Variable) {
+									if (((Variable) param).getType() == null) {
+										((Variable) param).setType(var.getType());
+									}
 								}
-							} else if (param instanceof Variable) {
-								if (((Variable) param).getType() == null) {
-									((Variable) param).setType(var.getType());
-								}
+								params.add(param.toImplementation(null));
+							} else {
+								params.add(var.getName());
 							}
-							params.add(param.toImplementation(null));
-						} else {
-							params.add(var.getName());
 						}
+						((Term) exp).replaceSubTerm(termEnt.getKey(), new Constant(langSpec.getConstructorInvocation(replacingClassName, params)));
+						subTerms = ((Term) exp).getSubTerms(Term.class);
+						termEntItr = subTerms.entrySet().iterator();
+					} else {
+						jsonTerm.setType(descendantType);
 					}
-					((Term) exp).replaceSubTerm(termEnt.getKey(), new Constant(langSpec.getConstructorInvocation(replacingClassName, params)));
-					subTerms = ((Term) exp).getSubTerms(Term.class);
-					termEntItr = subTerms.entrySet().iterator();
+				} else {
+					Type oldType = jsonTerm.getType();
+					Type newType = new Type(oldType.getTypeName(), 
+											oldType.getImplementationTypeName().replace(replacedJsonType.getInterfaceTypeName(), replacingClassName), 
+											oldType.getInterfaceTypeName().replace(replacedJsonType.getInterfaceTypeName(), replacingClassName));
+					for (Type parent: oldType.getParentTypes()) {
+						newType.addParentType(parent);
+					}
+					jsonTerm.setType(newType);
 				}
 			}
 		}
 		// Replace the type of the state field.
-		Type fieldType = getImplStateType(childRes.getParent(), langSpec);
+		Type fieldType = getImplStateType(descendantRes.getParent(), langSpec);
 		if (exp instanceof Term) {
 			((Term) exp).setType(fieldType);
 			for (Map.Entry<Position, Variable> varEnt: ((Term) exp).getVariables().entrySet()) {
diff --git a/AlgebraicDataflowArchitectureModel/src/generators/JavaMethodBodyGenerator.java b/AlgebraicDataflowArchitectureModel/src/generators/JavaMethodBodyGenerator.java
index c104e9c..59de1bd 100644
--- a/AlgebraicDataflowArchitectureModel/src/generators/JavaMethodBodyGenerator.java
+++ b/AlgebraicDataflowArchitectureModel/src/generators/JavaMethodBodyGenerator.java
@@ -889,42 +889,56 @@
 		return codes;
 	}
 
-	private static void replaceJsonTermWithConstructorInvocation(Expression exp, Type replacedJsonType, String replacingClassName, TypeDeclaration childComponent) {
+	private static void replaceJsonTermWithConstructorInvocation(Expression exp, Type replacedJsonType, String replacingClassName, TypeDeclaration descendantComponent) {
+		Type descendantType = new Type(replacingClassName, replacingClassName);
 		Map<Position, Term> subTerms = ((Term) exp).getSubTerms(Term.class);
 		Iterator<Entry<Position, Term>> termEntItr = subTerms.entrySet().iterator();
 		while (termEntItr.hasNext()) {
 			Entry<Position, Term> termEnt = termEntItr.next();
 			Term jsonTerm = termEnt.getValue();
-			if (jsonTerm.getType() != null && jsonTerm.getType().equals(replacedJsonType)) {
-				if (jsonTerm instanceof JsonTerm || jsonTerm.getSymbol().equals(DataConstraintModel.addMember)) {
-					String constructorInvocation = "new " + replacingClassName + "(";
-					MethodDeclaration childConstructor = getConstructor(childComponent);
-					String delimiter = "";
-					for (VariableDeclaration var: childConstructor.getParameters()) {
-						JsonAccessor jsonMember = new JsonAccessor(DataConstraintModel.dot);
-						jsonMember.addChild(jsonTerm);
-						jsonMember.addChild(new Constant(var.getName(), DataConstraintModel.typeString));
-						Expression param = jsonMember.reduce();
-						if (param != null) {
-							if (param instanceof Term) {
-								if (((Term) param).getType() == null) {
-									((Term) param).setType(var.getType());
+			if (jsonTerm.getType() != null) {
+				if (jsonTerm.getType().equals(replacedJsonType)) {
+					if (jsonTerm instanceof JsonTerm || jsonTerm.getSymbol().equals(DataConstraintModel.addMember)) {
+						String constructorInvocation = "new " + replacingClassName + "(";
+						MethodDeclaration descendantConstructor = getConstructor(descendantComponent);
+						String delimiter = "";
+						for (VariableDeclaration var: descendantConstructor.getParameters()) {
+							JsonAccessor jsonMember = new JsonAccessor(DataConstraintModel.dot);
+							jsonMember.addChild(jsonTerm);
+							jsonMember.addChild(new Constant(var.getName(), DataConstraintModel.typeString));
+							Expression param = jsonMember.reduce();
+							if (param != null) {
+								if (param instanceof Term) {
+									if (((Term) param).getType() == null) {
+										((Term) param).setType(var.getType());
+									}
+								} else if (param instanceof Variable) {
+									if (((Variable) param).getType() == null) {
+										((Variable) param).setType(var.getType());
+									}
 								}
-							} else if (param instanceof Variable) {
-								if (((Variable) param).getType() == null) {
-									((Variable) param).setType(var.getType());
-								}
+								constructorInvocation = constructorInvocation + delimiter + param.toImplementation(null);
+							} else {
+								constructorInvocation = constructorInvocation + delimiter + var.getName();
 							}
-							constructorInvocation = constructorInvocation + delimiter + param.toImplementation(null);
-						} else {
-							constructorInvocation = constructorInvocation + delimiter + var.getName();
+							delimiter = ", ";
 						}
-						delimiter = ", ";
+						constructorInvocation += ")";
+						((Term) exp).replaceSubTerm(termEnt.getKey(), new Constant(constructorInvocation, descendantType));
+						subTerms = ((Term) exp).getSubTerms(Term.class);
+						termEntItr = subTerms.entrySet().iterator();
+					} else {
+						jsonTerm.setType(descendantType);
 					}
-					constructorInvocation += ")";
-					((Term) exp).replaceSubTerm(termEnt.getKey(), new Constant(constructorInvocation));
-					subTerms = ((Term) exp).getSubTerms(Term.class);
-					termEntItr = subTerms.entrySet().iterator();
+				} else {
+					Type oldType = jsonTerm.getType();
+					Type newType = new Type(oldType.getTypeName(), 
+											oldType.getImplementationTypeName().replace(replacedJsonType.getInterfaceTypeName(), replacingClassName), 
+											oldType.getInterfaceTypeName().replace(replacedJsonType.getInterfaceTypeName(), replacingClassName));
+					for (Type parent: oldType.getParentTypes()) {
+						newType.addParentType(parent);
+					}
+					jsonTerm.setType(newType);
 				}
 			}
 		}
diff --git a/AlgebraicDataflowArchitectureModel/src/generators/JerseyMethodBodyGenerator.java b/AlgebraicDataflowArchitectureModel/src/generators/JerseyMethodBodyGenerator.java
index 1e4b295..47f4e58 100644
--- a/AlgebraicDataflowArchitectureModel/src/generators/JerseyMethodBodyGenerator.java
+++ b/AlgebraicDataflowArchitectureModel/src/generators/JerseyMethodBodyGenerator.java
@@ -1010,42 +1010,56 @@
 		return codes;
 	}
 
-	private static void replaceJsonTermWithConstructorInvocation(Expression exp, Type replacedJsonType, String replacingClassName, TypeDeclaration childComponent) {
+	private static void replaceJsonTermWithConstructorInvocation(Expression exp, Type replacedJsonType, String replacingClassName, TypeDeclaration descendantComponent) {
+		Type descendantType = new Type(replacingClassName, replacingClassName);
 		Map<Position, Term> subTerms = ((Term) exp).getSubTerms(Term.class);
 		Iterator<Entry<Position, Term>> termEntItr = subTerms.entrySet().iterator();
 		while (termEntItr.hasNext()) {
 			Entry<Position, Term> termEnt = termEntItr.next();
 			Term jsonTerm = termEnt.getValue();
-			if (jsonTerm.getType() != null && jsonTerm.getType().equals(replacedJsonType)) {
-				if (jsonTerm instanceof JsonTerm || jsonTerm.getSymbol().equals(DataConstraintModel.addMember)) {
-					String constructorInvocation = "new " + replacingClassName + "(";
-					MethodDeclaration childConstructor = getConstructor(childComponent);
-					String delimiter = "";
-					for (VariableDeclaration var: childConstructor.getParameters()) {
-						JsonAccessor jsonMember = new JsonAccessor(DataConstraintModel.dot);
-						jsonMember.addChild(jsonTerm);
-						jsonMember.addChild(new Constant(var.getName(), DataConstraintModel.typeString));
-						Expression param = jsonMember.reduce();
-						if (param != null) {
-							if (param instanceof Term) {
-								if (((Term) param).getType() == null) {
-									((Term) param).setType(var.getType());
+			if (jsonTerm.getType() != null) {
+				if (jsonTerm.getType().equals(replacedJsonType)) {
+					if (jsonTerm instanceof JsonTerm || jsonTerm.getSymbol().equals(DataConstraintModel.addMember)) {
+						String constructorInvocation = "new " + replacingClassName + "(";
+						MethodDeclaration descendantConstructor = getConstructor(descendantComponent);
+						String delimiter = "";
+						for (VariableDeclaration var: descendantConstructor.getParameters()) {
+							JsonAccessor jsonMember = new JsonAccessor(DataConstraintModel.dot);
+							jsonMember.addChild(jsonTerm);
+							jsonMember.addChild(new Constant(var.getName(), DataConstraintModel.typeString));
+							Expression param = jsonMember.reduce();
+							if (param != null) {
+								if (param instanceof Term) {
+									if (((Term) param).getType() == null) {
+										((Term) param).setType(var.getType());
+									}
+								} else if (param instanceof Variable) {
+									if (((Variable) param).getType() == null) {
+										((Variable) param).setType(var.getType());
+									}
 								}
-							} else if (param instanceof Variable) {
-								if (((Variable) param).getType() == null) {
-									((Variable) param).setType(var.getType());
-								}
+								constructorInvocation = constructorInvocation + delimiter + param.toImplementation(null);
+							} else {
+								constructorInvocation = constructorInvocation + delimiter + var.getName();
 							}
-							constructorInvocation = constructorInvocation + delimiter + param.toImplementation(null);
-						} else {
-							constructorInvocation = constructorInvocation + delimiter + var.getName();
+							delimiter = ", ";
 						}
-						delimiter = ", ";
+						constructorInvocation += ")";
+						((Term) exp).replaceSubTerm(termEnt.getKey(), new Constant(constructorInvocation));
+						subTerms = ((Term) exp).getSubTerms(Term.class);
+						termEntItr = subTerms.entrySet().iterator();
+					} else {
+						jsonTerm.setType(descendantType);
 					}
-					constructorInvocation += ")";
-					((Term) exp).replaceSubTerm(termEnt.getKey(), new Constant(constructorInvocation));
-					subTerms = ((Term) exp).getSubTerms(Term.class);
-					termEntItr = subTerms.entrySet().iterator();
+				} else {
+					Type oldType = jsonTerm.getType();
+					Type newType = new Type(oldType.getTypeName(), 
+											oldType.getImplementationTypeName().replace(replacedJsonType.getInterfaceTypeName(), replacingClassName), 
+											oldType.getInterfaceTypeName().replace(replacedJsonType.getInterfaceTypeName(), replacingClassName));
+					for (Type parent: oldType.getParentTypes()) {
+						newType.addParentType(parent);
+					}
+					jsonTerm.setType(newType);
 				}
 			}
 		}
diff --git a/AlgebraicDataflowArchitectureModel/src/models/algebra/Term.java b/AlgebraicDataflowArchitectureModel/src/models/algebra/Term.java
index 95c2b47..ac41269 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/algebra/Term.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/algebra/Term.java
@@ -295,22 +295,23 @@
 			String component0 = components[0].replace("(", "").replace(")", "");
 			String[] params = component0.split(",");
 			String exp = components[1];
+			String receiver = "";
 			if (implParamOrder == null) {
-				for (int i = 0; i < params.length; i++) {
+				receiver = children.get(0).toImplementation(sideEffects);
+				exp = exp.replace(params[0], receiver);
+				for (int i = 1; i < params.length; i++) {
 					exp = exp.replace(params[i], children.get(i).toImplementation(sideEffects));
 				}
 			} else {
-				for (int i = 0; i < params.length; i++) {
+				receiver = children.get(implParamOrder[0]).toImplementation(sideEffects);
+				exp = exp.replace(params[0], receiver);
+				for (int i = 1; i < params.length; i++) {
 					exp = exp.replace(params[i], children.get(implParamOrder[i]).toImplementation(sideEffects));
 				}
 			}
 			if (symbol.isImplWithSideEffect()) {
 				sideEffects[0] = sideEffects[0] + exp + ";\n";
-				if (implParamOrder == null) {
-					exp = children.get(0).toImplementation(new String[] {""});
-				} else {
-					exp = children.get(implParamOrder[0]).toImplementation(new String[] {""});
-				}
+				exp = receiver;
 			}
 			return exp;
 		}
@@ -333,7 +334,7 @@
 				String exp = symbol.generate(getType(), childrenTypes, childrenImpl, childrenSideEffects, sideEffects);
 				if (symbol.isImplWithSideEffect()) {
 					sideEffects[0] = sideEffects[0] + exp;
-					exp = children.get(0).toImplementation(new String[] {""});	// the value of this term
+					exp = childrenImpl[0];		// the value of this term
 				}
 				return exp;
 			} else {
@@ -351,7 +352,7 @@
 				String exp = symbol.generate(getType(), childrenTypes, childrenImpl, childrenSideEffects, sideEffects);
 				if (symbol.isImplWithSideEffect()) {
 					sideEffects[0] = sideEffects[0] + exp;
-					exp = children.get(implParamOrder[0]).toImplementation(new String[] {""});	// the value of this term
+					exp = childrenImpl[0];		// the value of this term
 				}
 				return exp;
 			}
@@ -360,14 +361,16 @@
 			if (implParamOrder == null) {
 				return "(" + children.get(0).toImplementation(sideEffects) + symbol.toImplementation() + children.get(1).toImplementation(sideEffects) + ")";
 			} else {
-				return "(" + children.get(implParamOrder[0]).toImplementation(sideEffects) + symbol.toImplementation() + children.get(implParamOrder[1]).toImplementation(sideEffects) + ")";				
+				return "(" + children.get(implParamOrder[0]).toImplementation(sideEffects) + symbol.toImplementation() + children.get(implParamOrder[1]).toImplementation(sideEffects) + ")";
 			}
 		}
 		if ((getArity() >= 1 || getArity() == -1) && symbol.isImplMethod()) {
 			if (implParamOrder == null) {
 				String exp = null;
+				String receiver = "";
 				if (children.get(0) != null) {
-					exp = children.get(0).toImplementation(sideEffects) + "." + symbol.toImplementation() + "(";
+					receiver = children.get(0).toImplementation(sideEffects);
+					exp = receiver + "." + symbol.toImplementation() + "(";
 				} else {
 					exp = symbol.toImplementation() + "(";
 				}
@@ -380,15 +383,12 @@
 				exp += ")";
 				if (symbol.isImplWithSideEffect()) {
 					sideEffects[0] = sideEffects[0] + exp + ";\n";
-					if (children.get(0) != null) {
-						exp = children.get(0).toImplementation(new String[] {""});
-					} else {
-						exp = "";
-					}
+					exp = receiver;
 				}
 				return exp;
 			} else {
-				String exp = children.get(implParamOrder[0]).toImplementation(sideEffects) + "." + symbol.toImplementation() + "(";
+				String receiver = children.get(implParamOrder[0]).toImplementation(sideEffects);
+				String exp = receiver + "." + symbol.toImplementation() + "(";
 				String delimiter = "";
 				for (int i = 1; i < children.size(); i++) {
 					Expression e = children.get(implParamOrder[i]);
@@ -398,7 +398,7 @@
 				exp += ")";
 				if (symbol.isImplWithSideEffect()) {
 					sideEffects[0] = sideEffects[0] + exp + ";\n";
-					exp = children.get(implParamOrder[0]).toImplementation(new String[] {""});
+					exp = receiver;
 				}
 				return exp;
 			}
diff --git a/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java b/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
index 3bdb1dd..555f07d 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
@@ -676,6 +676,7 @@
 		}
 	});
 	public static final Symbol nil = new Symbol("nil", 0, Symbol.Type.PREFIX, new Symbol.IImplGenerator() {
+		final int count[] = {0};
 		@Override
 		public String generate(Type type, Type[] childrenTypes, String[] children, String[] childrenSideEffects, String[] sideEffect) {
 			String compType = "";
@@ -691,14 +692,18 @@
 				if (sideEffect == null) {
 					return "new " + implType + "<>()";
 				} else {
-					String temp = "temp_nil";
-					sideEffect[0] = interfaceType + " " + temp + " = " + "new " + implType + "<" + compType + ">();\n";
+					String temp = "temp_nil" + count[0];
+					if (sideEffect[0] == null) {
+						sideEffect[0] = "";
+					}
+					sideEffect[0] += interfaceType + " " + temp + " = " + "new " + implType + "<" + compType + ">();\n";
+					count[0]++;
 					return temp;
 				}
 			}			
 			return "new ArrayList<" + compType + ">()";
 		}
-	});
+	}, true);
 	public static final Symbol null_ = new Symbol("null", 0, Symbol.Type.PREFIX, "null", Symbol.Type.PREFIX);
 	public static final Symbol true_ = new Symbol("true", 0, Symbol.Type.PREFIX, "true", Symbol.Type.PREFIX);
 	public static final Symbol false_ = new Symbol("false", 0, Symbol.Type.PREFIX, "false", Symbol.Type.PREFIX);