ParentObject name {
       Property1 = "Test";
       Property2 = "Test2";
       // ...

       ChildObject name {
               PropertyA = "ABC";
               PropertyB = "CDE";
               // ...
       }
}

ParentObject name {
       Property2 = "Test";
       Property1 = "Test2";
       // ...

       ChildObject name {
               PropertyB = "ABC";
               PropertyA = "CDE";
               // ...
       }
}

class ParentObject {
        String propertyA
        int   propertyB
}

ParentObject:
      'ParentObject' name=ID '{'
               'PropertyA' '=' propertyA=STRING ';'
               'PropertyB' '=' propertyB=INT ';'
      '}';

class Property {
       String name
}

class StringProperty extends Property {
        String value
}

class IntProperty  extends Property {
        int value
}

class PropertyA extends StringProperty {}

class PropertyB extends IntProperty {}

class ParentObject {
      contains Property[*] properties
}

ParentObject:
      'ParentObject' name=ID '{'
               (PropertyA | PropertyB)*
      '}';
PropertyA:   name='PropertyA' value=STRING;
PropertyB:   name='PropertyB' value=INT;

modelObject.propertyA

modelObject.properties.filter[it instanceof PropertyA].head.value

def getPropertyA (ParentObject modelObject) {
   modelObject.properties.filter[it instanceof PropertyA].head.value
}

modelObject.propertyA

Could not serialize Task via backtracking.
Constraint: Task_Task returns Task: (
  name=ID
  (
        properties+=RAMUtilizationProperty |
        properties+=ROMUtilizationProperty |
        properties+=DurationProperty  |
        ...
  )*
);
Values: name(1), properties(4)
Semantic Object: AssistModel.applications[0]->Application'A1'.tasks[0] ->Task'A1_T1' 
URI: platform:/resource/ExampleSystem/Scheduling/newSpec.sdsl
Context: Task returns Task