diff --git a/AlgebraicDataflowArchitectureModel/models/NemophilaAccounts.model b/AlgebraicDataflowArchitectureModel/models/NemophilaAccounts.model
index c2cc23a..0158d26 100644
--- a/AlgebraicDataflowArchitectureModel/models/NemophilaAccounts.model
+++ b/AlgebraicDataflowArchitectureModel/models/NemophilaAccounts.model
@@ -36,7 +36,7 @@
 	out accounts.{sendId}.requesting(sendRequesting:Map, sync1(recvId:Str, sendRequested:Map, recvRequesting:Map, sendFriends:Map)) = if(contains(sendFriends:Map, recvId) == true,
 																																		sendRequesting,
 																																		insert(sendRequesting:Map, recvId:Str, true))
-	out accounts.{recvId}.requested(recvRequested:Map, sync1(recvId:Str, sendRequested:Map, recvRequesting:Map, sendFriends:Map)) = if(ontains(sendFriends:Map, recvId) == true,
+	out accounts.{recvId}.requested(recvRequested:Map, sync1(recvId:Str, sendRequested:Map, recvRequesting:Map, sendFriends:Map)) = if(contains(sendFriends:Map, recvId) == true,
 																																		recvRequested,
 																																		insert(recvRequested:Map, sendId:Str, true))
 }
diff --git a/AlgebraicDataflowArchitectureModel/src/generators/CodeGeneratorFromDataFlowGraph.java b/AlgebraicDataflowArchitectureModel/src/generators/CodeGeneratorFromDataFlowGraph.java
index 51abab3..45c2652 100644
--- a/AlgebraicDataflowArchitectureModel/src/generators/CodeGeneratorFromDataFlowGraph.java
+++ b/AlgebraicDataflowArchitectureModel/src/generators/CodeGeneratorFromDataFlowGraph.java
@@ -262,7 +262,7 @@
 										((Variable) param).setType(var.getType());
 									}
 								}
-								params.add(param.toImplementation(null));
+								params.add(param.toImplementation(new String[] {""}));
 							} else {
 								params.add(var.getName());
 							}
diff --git a/AlgebraicDataflowArchitectureModel/src/generators/JavaMethodBodyGenerator.java b/AlgebraicDataflowArchitectureModel/src/generators/JavaMethodBodyGenerator.java
index 59de1bd..c56d194 100644
--- a/AlgebraicDataflowArchitectureModel/src/generators/JavaMethodBodyGenerator.java
+++ b/AlgebraicDataflowArchitectureModel/src/generators/JavaMethodBodyGenerator.java
@@ -216,7 +216,7 @@
 												}
 												v++;
 											}
-											String ifStatement = "if (" + conditions.toImplementation(new String[] {})+ ") {\n";
+											String ifStatement = "if (" + conditions.toImplementation(new String[] {""})+ ") {\n";
 											update.addFirstStatement(ifStatement + "\t" + updateStatement.replace("\n", "\n\t") + "\n}");
 										}
 									}
@@ -632,7 +632,7 @@
 											composerSub = composer;
 										}
 										composer.setType(stateGetter.getReturnType());
-										String[] sideEffects = new String[] {null};
+										String[] sideEffects = new String[] {""};
 										String returnValue = composer.toImplementation(sideEffects);
 										if (sideEffects[0] != null) {
 											stateGetter.addStatement(sideEffects[0] + "return " + returnValue+ ";");
diff --git a/AlgebraicDataflowArchitectureModel/src/generators/JerseyMethodBodyGenerator.java b/AlgebraicDataflowArchitectureModel/src/generators/JerseyMethodBodyGenerator.java
index 47f4e58..5f8615b 100644
--- a/AlgebraicDataflowArchitectureModel/src/generators/JerseyMethodBodyGenerator.java
+++ b/AlgebraicDataflowArchitectureModel/src/generators/JerseyMethodBodyGenerator.java
@@ -237,7 +237,7 @@
 												}
 												v++;
 											}
-											String ifStatement = "if (" + conditions.toImplementation(new String[] {})+ ") {\n";
+											String ifStatement = "if (" + conditions.toImplementation(new String[] {""})+ ") {\n";
 											update.addFirstStatement(ifStatement + "\t" + updateStatement.replace("\n", "\n\t") + "\n}");
 										}
 									}
@@ -281,7 +281,7 @@
 												}
 												resExp = ((Term) resExp).getChild(0);
 											}
-											String resourceAccess = resExp.toImplementation(new String[] {null});
+											String resourceAccess = resExp.toImplementation(new String[] {""});
 											int v = 0;
 											for (VariableDeclaration var: update2.getParameters()) {
 												if (v < out.getResource().getPathParams().size()) {
@@ -811,7 +811,7 @@
 											params++;
 										}
 										if (descendantGetter != null && (descendantGetter.getBody() == null || descendantGetter.getBody().getStatements().size() == 0)) {
-											String[] sideEffects = new String[] {null};
+											String[] sideEffects = new String[] {""};
 											String returnValue = selector.toImplementation(sideEffects);
 											if (sideEffects[0] != null) descendantGetter.addStatement(sideEffects[0]);
 											descendantGetter.addStatement("return " + returnValue + ";");
@@ -977,7 +977,7 @@
 										}
 										resExp = ((Term) resExp).getChild(0);
 									}
-									String resourceAccess = resExp.toImplementation(new String[] {null});
+									String resourceAccess = resExp.toImplementation(new String[] {""});
 									// Values of channel parameters.
 									for (Selector selector: ch.getAllSelectors()) {
 										if (selector.getExpression() instanceof Variable) {
@@ -1038,7 +1038,7 @@
 										((Variable) param).setType(var.getType());
 									}
 								}
-								constructorInvocation = constructorInvocation + delimiter + param.toImplementation(null);
+								constructorInvocation = constructorInvocation + delimiter + param.toImplementation(new String[] {""});
 							} else {
 								constructorInvocation = constructorInvocation + delimiter + var.getName();
 							}
diff --git a/AlgebraicDataflowArchitectureModel/src/models/algebra/Parameter.java b/AlgebraicDataflowArchitectureModel/src/models/algebra/Parameter.java
index 739ab80..b567ecb 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/algebra/Parameter.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/algebra/Parameter.java
@@ -20,7 +20,7 @@
 	}
 	
 	public Type getType() {
-		if (symbol.getSignature().length >= 1) {
+		if (symbol.getSignature() != null && symbol.getSignature().length >= 1) {
 			return symbol.getSignature()[0];
 		}
 		return null;
diff --git a/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java b/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
index fcd5ccc..903c152 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
@@ -233,7 +233,8 @@
 			for (String s: childrenSideEffects) {
 				sideEffect[0] += s;
 			}
-			if (childrenTypes[0].equals(typeString) && childrenTypes[1].equals(typeString)) {
+			if (childrenTypes[0] != null && childrenTypes[0].equals(typeString) 
+					&& childrenTypes[1] != null && childrenTypes[1].equals(typeString)) {
 				return children[0] + ".equals(" + children[1] + ")";
 			}
 			return "(" + children[0] + "==" + children[1] + ")";