diff --git a/AlgebraicDataflowArchitectureModel/models/SimpleUI.model b/AlgebraicDataflowArchitectureModel/models/SimpleUI.model
index 9b54346..3e03bbd 100644
--- a/AlgebraicDataflowArchitectureModel/models/SimpleUI.model
+++ b/AlgebraicDataflowArchitectureModel/models/SimpleUI.model
@@ -1,7 +1,12 @@
 init {
-	screen := {"widgets": {"001": {"type": "button", "text": "OK", "state": 0}, 
-							"002": {"type": "textInput", "text": "", "state": 0}}, 
-				"layout": true}
+	screenTemplates := {
+				"000": {"widgets": {"001": {"type": "textInput", "text": "", "state": 0}, 
+									"002": {"type": "button", "text": "Next", "state": 0}}, 
+						"layout": true},
+				"001": {"widgets": {"003": {"type": "label", "text": "label", "state": 0}, 
+									"004": {"type": "button", "text": "Back", "state": 0}}, 
+						"layout": true}
+				}
 }
 
 native channel ScreenUpdate {
@@ -44,6 +49,16 @@
 	out screen.widgets.{wid}.text(curText: Str, textEvent(nextText)) = nextText
 }
 
+channel ChangeCurScreen {
+	out curScreen(curScId: Str, changeCurScreen(nextScId)) = nextScId
+}
+
+channel ScreenTransition {
+	in curScreen(curScId: Str, transScreen(nextScId, nextSc)) = nextScId
+	in screenTemplates.{nextScId}(curSc, transScreen(nextScId, nextSc)) = nextSc
+	out screen(curS, transScreen(nextScId, nextSc)) = nextSc
+}
+
 channel ChangeLayout {
 	out screen.layout(curLayout: Bool, changeLayout(layout)) = layout
 }
@@ -78,4 +93,4 @@
 
 channel AddMovableTextInput {
 	out screen.widgets(widgets: Map, addMovableTextInput(wid: Str, x: Int, y: Int, width: Int, height: Int)) = insert(widgets, wid, {"type": "textInput", "text": "", "x": x, "y": y, "width": width, "height": height, "state": 0})
-}
+}
\ No newline at end of file
diff --git a/AlgebraicDataflowArchitectureModel/src/models/algebra/Symbol.java b/AlgebraicDataflowArchitectureModel/src/models/algebra/Symbol.java
index 20c3cf2..980fc53 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/algebra/Symbol.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/algebra/Symbol.java
@@ -51,6 +51,7 @@
 	
 	public Symbol(String name, int arity, Type operatorType, IImplGenerator generator) {
 		this.name = name;
+		this.implName = name;
 		this.arity = arity;
 		this.operatorType = operatorType;
 		this.generator = generator;
@@ -59,6 +60,7 @@
 	
 	public Symbol(String name, int arity, Type operatorType, IImplGenerator generator, boolean bSideEffect) {
 		this.name = name;
+		this.implName = name;
 		this.arity = arity;
 		this.operatorType = operatorType;
 		this.generator = generator;
@@ -71,19 +73,23 @@
 	
 	public Symbol(String name, int arity, ICalculator calculator) {
 		this.name = name;
+		this.implName = name;
 		this.arity = arity;
 		this.calculator = calculator;
 	}
 	
 	public Symbol(String name, int arity, Type operatorType, ICalculator calculator) {
 		this.name = name;
+		this.implName = name;
 		this.arity = arity;
 		this.operatorType = operatorType;
+		this.implOperatorType = operatorType;
 		this.calculator = calculator;
 	}
 	
 	public Symbol(String name, int arity, Type operatorType, IImplGenerator generator, ICalculator calculator) {
 		this.name = name;
+		this.implName = name;
 		this.arity = arity;
 		this.operatorType = operatorType;
 		this.generator = generator;
diff --git a/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java b/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
index a76879f..4482a27 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
@@ -40,10 +40,10 @@
 	public static final Symbol add = new Symbol(Parser.ADD, 2, Symbol.Type.INFIX, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (!(args.get(0) instanceof Constant)) {
+			if (!(args.get(0).getClass() == Constant.class)) {
 				return null;
 			}
-			if (!(args.get(1) instanceof Constant)) {
+			if (!(args.get(1).getClass() == Constant.class)) {
 				return null;
 			}
 			Constant arg0 = (Constant) args.get(0);
@@ -65,10 +65,10 @@
 	public static final Symbol mul = new Symbol(Parser.MUL, 2, Symbol.Type.INFIX, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (!(args.get(0) instanceof Constant)) {
+			if (!(args.get(0).getClass() == Constant.class)) {
 				return null;
 			}
-			if (!(args.get(1) instanceof Constant)) {
+			if (!(args.get(1).getClass() == Constant.class)) {
 				return null;
 			}
 			Constant arg0 = (Constant) args.get(0);
@@ -90,10 +90,10 @@
 	public static final Symbol sub = new Symbol(Parser.SUB, 2, Symbol.Type.INFIX, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (!(args.get(0) instanceof Constant)) {
+			if (!(args.get(0).getClass() == Constant.class)) {
 				return null;
 			}
-			if (!(args.get(1) instanceof Constant)) {
+			if (!(args.get(1).getClass() == Constant.class)) {
 				return null;
 			}
 			Constant arg0 = (Constant) args.get(0);
@@ -115,10 +115,10 @@
 	public static final Symbol div = new Symbol(Parser.DIV, 2, Symbol.Type.INFIX, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (!(args.get(0) instanceof Constant)) {
+			if (!(args.get(0).getClass() == Constant.class)) {
 				return null;
 			}
-			if (!(args.get(1) instanceof Constant)) {
+			if (!(args.get(1).getClass() == Constant.class)) {
 				return null;
 			}
 			Constant arg0 = (Constant) args.get(0);
@@ -140,10 +140,10 @@
 	public static final Symbol mod = new Symbol(Parser.MOD, 2, Symbol.Type.INFIX, "%", Symbol.Type.INFIX, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (!(args.get(0) instanceof Constant)) {
+			if (!(args.get(0).getClass() == Constant.class)) {
 				return null;
 			}
-			if (!(args.get(1) instanceof Constant)) {
+			if (!(args.get(1).getClass() == Constant.class)) {
 				return null;
 			}
 			Constant arg0 = (Constant) args.get(0);
@@ -161,7 +161,7 @@
 	public static final Symbol minus = new Symbol(Parser.MINUS, 1, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (!(args.get(0) instanceof Constant)) {
+			if (!(args.get(0).getClass() == Constant.class)) {
 				return null;
 			}
 			Constant arg = (Constant) args.get(0);
@@ -193,10 +193,10 @@
 	}, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (!(args.get(0) instanceof Constant)) {
+			if (!(args.get(0).getClass() == Constant.class)) {
 				return null;
 			}
-			if (!(args.get(1) instanceof Constant)) {
+			if (!(args.get(1).getClass() == Constant.class)) {
 				return null;
 			}
 			Constant arg0 = (Constant) args.get(0);
@@ -237,10 +237,10 @@
 	}, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (!(args.get(0) instanceof Constant)) {
+			if (!(args.get(0).getClass() == Constant.class)) {
 				return null;
 			}
-			if (!(args.get(1) instanceof Constant)) {
+			if (!(args.get(1).getClass() == Constant.class)) {
 				return null;
 			}
 			Constant arg0 = (Constant) args.get(0);
@@ -269,10 +269,10 @@
 	public static final Symbol gt = new Symbol(Parser.GT, 2, Symbol.Type.INFIX, ">", Symbol.Type.INFIX, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (!(args.get(0) instanceof Constant)) {
+			if (!(args.get(0).getClass() == Constant.class)) {
 				return null;
 			}
-			if (!(args.get(1) instanceof Constant)) {
+			if (!(args.get(1).getClass() == Constant.class)) {
 				return null;
 			}
 			Constant arg0 = (Constant) args.get(0);
@@ -299,10 +299,10 @@
 	public static final Symbol lt = new Symbol(Parser.LT, 2, Symbol.Type.INFIX, "<", Symbol.Type.INFIX, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (!(args.get(0) instanceof Constant)) {
+			if (!(args.get(0).getClass() == Constant.class)) {
 				return null;
 			}
-			if (!(args.get(1) instanceof Constant)) {
+			if (!(args.get(1).getClass() == Constant.class)) {
 				return null;
 			}
 			Constant arg0 = (Constant) args.get(0);
@@ -329,10 +329,10 @@
 	public static final Symbol ge = new Symbol(Parser.GE, 2, Symbol.Type.INFIX, ">=", Symbol.Type.INFIX, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (!(args.get(0) instanceof Constant)) {
+			if (!(args.get(0).getClass() == Constant.class)) {
 				return null;
 			}
-			if (!(args.get(1) instanceof Constant)) {
+			if (!(args.get(1).getClass() == Constant.class)) {
 				return null;
 			}
 			Constant arg0 = (Constant) args.get(0);
@@ -359,10 +359,10 @@
 	public static final Symbol le = new Symbol(Parser.LE, 2, Symbol.Type.INFIX, "<=", Symbol.Type.INFIX, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (!(args.get(0) instanceof Constant)) {
+			if (!(args.get(0).getClass() == Constant.class)) {
 				return null;
 			}
-			if (!(args.get(1) instanceof Constant)) {
+			if (!(args.get(1).getClass() == Constant.class)) {
 				return null;
 			}
 			Constant arg0 = (Constant) args.get(0);
@@ -389,10 +389,10 @@
 	public static final Symbol and = new Symbol(Parser.AND, 2, Symbol.Type.INFIX, "&&", Symbol.Type.INFIX, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (!(args.get(0) instanceof Constant)) {
+			if (!(args.get(0).getClass() == Constant.class)) {
 				return null;
 			}
-			if (!(args.get(1) instanceof Constant)) {
+			if (!(args.get(1).getClass() == Constant.class)) {
 				return null;
 			}
 			Constant arg0 = (Constant) args.get(0);
@@ -413,10 +413,10 @@
 	public static final Symbol or = new Symbol(Parser.OR, 2, Symbol.Type.INFIX, "||", Symbol.Type.INFIX, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (!(args.get(0) instanceof Constant)) {
+			if (!(args.get(0).getClass() == Constant.class)) {
 				return null;
 			}
-			if (!(args.get(1) instanceof Constant)) {
+			if (!(args.get(1).getClass() == Constant.class)) {
 				return null;
 			}
 			Constant arg0 = (Constant) args.get(0);
@@ -437,7 +437,7 @@
 	public static final Symbol neg = new Symbol(Parser.NEG, 1, Symbol.Type.PREFIX, "!", Symbol.Type.PREFIX, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (!(args.get(0) instanceof Constant)) {
+			if (!(args.get(0).getClass() == Constant.class)) {
 				return null;
 			}
 			Constant arg0 = (Constant) args.get(0);
@@ -475,7 +475,7 @@
 	}, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (args.get(0) instanceof Constant && ((Constant) args.get(0)).getSymbol().equals(nil)) {
+			if (args.get(0).getClass() == Constant.class && ((Constant) args.get(0)).getSymbol().equals(nil)) {
 				return new Constant(false_);
 			}
 			if (args.get(0) instanceof Term) {
@@ -588,7 +588,7 @@
 	}, new Symbol.ICalculator() {
 		@Override
 		public Expression calculate(List<Expression> args) {
-			if (!(args.get(0) instanceof Constant)) return null;
+			if (!(args.get(0).getClass() == Constant.class)) return null;
 			if (((Constant) args.get(0)).getSymbol().equals(true_)) {
 				return args.get(1);
 			} else if (((Constant) args.get(0)).getSymbol().equals(false_)) {