diff --git a/AlgebraicDataflowArchitectureModel/src/generators/JavaCodeGenerator.java b/AlgebraicDataflowArchitectureModel/src/generators/JavaCodeGenerator.java
index 32b9289..a15057e 100644
--- a/AlgebraicDataflowArchitectureModel/src/generators/JavaCodeGenerator.java
+++ b/AlgebraicDataflowArchitectureModel/src/generators/JavaCodeGenerator.java
@@ -1088,11 +1088,7 @@
 		if (res.getInitialValue() != null) {
 			initializer = res.getInitialValue().toImplementation(new String[] {""});
 		} else if (stateType != null) {
-			if (DataConstraintModel.typeList.isAncestorOf(stateType)) {
-				initializer = "new " + res.getResourceStateType().getImplementationTypeName() + "()";
-			} else if (DataConstraintModel.typeMap.isAncestorOf(stateType)) {
-				initializer = "new " + res.getResourceStateType().getImplementationTypeName() + "()";
-			}
+			initializer = DataConstraintModel.getDefaultValue(stateType);
 		}
 		return initializer;
 	}
diff --git a/AlgebraicDataflowArchitectureModel/src/generators/JavaSpecific.java b/AlgebraicDataflowArchitectureModel/src/generators/JavaSpecific.java
index 72d79a9..6134a5f 100644
--- a/AlgebraicDataflowArchitectureModel/src/generators/JavaSpecific.java
+++ b/AlgebraicDataflowArchitectureModel/src/generators/JavaSpecific.java
@@ -106,11 +106,7 @@
 		if (initialValue != null) {
 			initializer = initialValue.toImplementation(new String[] {""});
 		} else if (type != null) {
-			if (DataConstraintModel.typeList.isAncestorOf(type)) {
-				initializer = "new " + type.getImplementationTypeName() + "()";
-			} else if (DataConstraintModel.typeMap.isAncestorOf(type)) {
-				initializer = "new " + type.getImplementationTypeName() + "()";
-			}
+			initializer = DataConstraintModel.getDefaultValue(type);
 		}
 		return initializer;
 	}
diff --git a/AlgebraicDataflowArchitectureModel/src/generators/JerseyCodeGenerator.java b/AlgebraicDataflowArchitectureModel/src/generators/JerseyCodeGenerator.java
index 151ab6e..2d1c1c2 100644
--- a/AlgebraicDataflowArchitectureModel/src/generators/JerseyCodeGenerator.java
+++ b/AlgebraicDataflowArchitectureModel/src/generators/JerseyCodeGenerator.java
@@ -1165,12 +1165,8 @@
 		String initializer = null;
 		if (res.getInitialValue() != null) {
 			initializer = res.getInitialValue().toImplementation(new String[] {""});
-		} else {
-			if (DataConstraintModel.typeList.isAncestorOf(stateType)) {
-				initializer = "new " + res.getResourceStateType().getImplementationTypeName() + "()";
-			} else if (DataConstraintModel.typeMap.isAncestorOf(stateType)) {
-				initializer = "new " + res.getResourceStateType().getImplementationTypeName() + "()";
-			}
+		} else if (stateType != null) {
+			initializer = DataConstraintModel.getDefaultValue(stateType);
 		}
 		return initializer;
 	}
diff --git a/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java b/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
index 3a3de81..e44c50c 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
@@ -884,9 +884,28 @@
 	public static final Symbol addMember = new Symbol("addMember", 3, Symbol.Type.PREFIX, "put", Symbol.Type.METHOD_WITH_SIDE_EFFECT);
 	public static final Symbol dot = new Symbol(Parser.DOT, 2, Symbol.Type.INFIX, "get", Symbol.Type.METHOD);
 	public static final Symbol dotParam = new Symbol(Parser.DOT, 2, Symbol.Type.INFIX, "get", Symbol.Type.METHOD);
-	public static final Symbol pi = new Symbol("PI", 0, Symbol.Type.PREFIX, "Math.PI", Symbol.Type.PREFIX);
-	public static final Symbol E = new Symbol("E", 0, Symbol.Type.PREFIX, "Math.E", Symbol.Type.PREFIX);
-	public static final Symbol sqrt = new Symbol("sqrt", 1, Symbol.Type.PREFIX, "Math.sqrt", Symbol.Type.PREFIX);
+	public static final Symbol pi = new Symbol("PI", 0, Symbol.Type.PREFIX, "Math.PI", Symbol.Type.PREFIX, new Symbol.ICalculator() {
+		@Override
+		public Expression calculate(List<Expression> args) {
+			return new Constant(Double.toString(Math.PI), typeDouble);
+		}});
+	public static final Symbol E = new Symbol("E", 0, Symbol.Type.PREFIX, "Math.E", Symbol.Type.PREFIX, new Symbol.ICalculator() {
+		@Override
+		public Expression calculate(List<Expression> args) {
+			return new Constant(Double.toString(Math.E), typeDouble);
+		}});
+	public static final Symbol sqrt = new Symbol("sqrt", 1, Symbol.Type.PREFIX, "Math.sqrt", Symbol.Type.PREFIX, new Symbol.ICalculator() {
+		@Override
+		public Expression calculate(List<Expression> args) {
+			if (args.get(0).getClass() == Constant.class) {
+				if (((Constant) args.get(0)).getType().equals(typeDouble)) {
+					return new Constant(Double.toString(Math.sqrt(Double.parseDouble((String) ((Constant) args.get(0)).getValue()))), typeDouble);
+				} else if (((Constant) args.get(0)).getType().equals(typeFloat)) {
+					return new Constant(Float.toString((float) Math.sqrt(Float.parseFloat((String) ((Constant) args.get(0)).getValue()))), typeFloat);
+				}
+			}
+			return null;
+		}});
 	public static final Symbol sin = new Symbol("sin", 1, Symbol.Type.PREFIX, "Math.sin", Symbol.Type.PREFIX);
 	public static final Symbol cos = new Symbol("cos", 1, Symbol.Type.PREFIX, "Math.cos", Symbol.Type.PREFIX);
 	public static final Symbol tan = new Symbol("tan", 1, Symbol.Type.PREFIX, "Math.tan", Symbol.Type.PREFIX);
@@ -1206,6 +1225,29 @@
 		return "new " + type.getImplementationTypeName() + "()";
 	}
 	
+	public static Expression getDefaultValueExpression(Type type) {
+		if (type == typeInt) {
+			return new Constant("0", typeInt);
+		} else if (type == typeLong) {
+			return new Constant("0L", typeLong);
+		} else if (type == typeFloat) {
+			return new Constant("0.0f", typeFloat);
+		} else if (type == typeDouble) {
+			return new Constant("0.0", typeDouble);
+		} else if (type == typeBoolean) {
+			return new Constant(false_);
+		} else if (type == typeString) {
+			return new Constant("", typeString);
+		} else if (type.isAncestorOf(typeList)) {
+			return new ListTerm();
+		} else if (type.isAncestorOf(typeMap)) {
+			return new MapTerm();
+		} else if (type.isAncestorOf(typeJson)) {
+			return new JsonTerm();
+		}
+		return null;
+	}
+	
 	@Override
 	public String toString() {
 		String out = "";
diff --git a/AlgebraicDataflowArchitectureModel/src/simulator/Simulator.java b/AlgebraicDataflowArchitectureModel/src/simulator/Simulator.java
index d1a5359..a2df91d 100644
--- a/AlgebraicDataflowArchitectureModel/src/simulator/Simulator.java
+++ b/AlgebraicDataflowArchitectureModel/src/simulator/Simulator.java
@@ -18,6 +18,7 @@
 import models.algebra.Variable;
 import models.dataConstraintModel.Channel;
 import models.dataConstraintModel.ChannelMember;
+import models.dataConstraintModel.DataConstraintModel;
 import models.dataConstraintModel.ResourceHierarchy;
 import models.dataConstraintModel.ResourcePath;
 import models.dataConstraintModel.Selector;
@@ -59,6 +60,11 @@
 						initialValue = ((Term) initialValue).reduce();
 					}
 					curState.updateResourceState(resource.getResourceIdentifier(), null, null, initialValue);
+				} else if (res.getResourceStateType() != null) {
+					initialValue = DataConstraintModel.getDefaultValueExpression(res.getResourceStateType());
+					if (initialValue != null) {
+						curState.updateResourceState(resource.getResourceIdentifier(), null, null, initialValue);
+					}
 				}
 			}
 		}
@@ -195,7 +201,7 @@
 				Expression nextResState = null;
 				outTarget[0] = out;
 				outResVar[0] = new Variable(channel.getChannelName() + "$" + out.getResource().toString() + "$this");		// A special variable to represent the current state of each output resource.
-				if (!event.isInput()) {
+				if (!event.isInput() || event.getMessage() instanceof Variable) {
 					nextResState = channel.deriveUpdateExpressionOf(out, resouceStateAccessor).getKey();
 				} else {
 					nextResState = channel.deriveUpdateExpressionOf(out, (Term) event.getMessage(), resouceStateAccessor);