diff --git a/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java b/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
index 6ce02cd..4a498b1 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/dataConstraintModel/DataConstraintModel.java
@@ -1,6 +1,7 @@
 package models.dataConstraintModel;
 
 import java.util.AbstractMap;
+import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
@@ -76,6 +77,8 @@
 					return new Constant(Long.toString(Long.parseLong(sArg0) + Long.parseLong(sArg1)), typeLong);
 				} else if (arg0.getType().equals(typeInt) || arg1.getType().equals(typeInt)) {
 					return new Constant(Integer.toString(Integer.parseInt(sArg0) + Integer.parseInt(sArg1)), typeInt);
+				} else if (arg0.getType().equals(typeString) || arg1.getType().equals(typeString)) {
+					return new Constant((String) arg0.getValue() + (String) arg1.getValue(), typeString);
 				}
 			}
 			if (sArg0.contains(Parser.DOT) || sArg1.contains(Parser.DOT)) {
@@ -595,6 +598,21 @@
 						keySet.addAll(((JsonTerm) term).keySet());
 						return new Constant(Integer.toString(keySet.size()), typeInt);
 					}
+				} else if (typeString.isAncestorOf(type)) {
+					int len = 0;
+					ArrayDeque<Term> strTerms = new ArrayDeque<>();
+					strTerms.add(term);
+					while (strTerms.size() > 0) {
+						term = strTerms.poll();
+						type = term.getType();
+						if (term.getSymbol().equals(DataConstraintModel.add)) {
+							strTerms.add((Term) term.getChild(0));
+							strTerms.add((Term) term.getChild(1));
+						} else if (term instanceof Constant && typeString.isAncestorOf(type)) {
+							len += ((String) ((Constant) term).getValue()).length();
+						}
+					}
+					return new Constant(Integer.toString(len), typeInt);
 				}
 			}
 			return null;