SimpleClassDiagrams PetriNetsPorts {
    SimpleAttribute Integer{
        constraint = $
            String function constraint(model : Element, name : String):
                if (is_physical_int(model["model"][name])):
                    return "OK"!
                else:
                    return "Integer has non-integer value"!
    }

    SimpleAttribute String{
        constraint = $
            String function constraint(model : Element, name : String):
                if (is_physical_string(model["model"][name])):
                    return "OK"!
                else:
                    return "String has non-string value"!
            $
    }

    SimpleAttribute PlaceOrTransition{
        constraint = $
            String function constraint(model : Element, name : String):
                if (is_physical_string(model["model"][name])):
                    if (boolean_or(value_eq(model["model"][name], "transition"), value_eq(model["model"][name], "place"))):
                        return "OK"!
                    else:
                        return "PlaceOrTransition does not contain either 'place' or 'transition'"!
                else:
                    return "PlaceOrTransition has non-string value"!
            $
    }
    Class Positionable {
        x : Integer
        y : Integer
    }
    Class Named {
        name : String
    }
    Class Boundary : Named, Positionable {}
    Class Place : Positionable, Named {
        nbTokens : Integer
    }
    Class Transition : Positionable, Named {}
    Class Port : Named, Positionable {
        sourceType : PlaceOrTransition
        targetType : PlaceOrTransition
    }

    Association Has1 (Boundary, Place) {}
    Association Has2 (Boundary, Transition) {}
    Association Has3 (Boundary, Port) {}
    Association P2T (Place, Transition) {}
    Association T2P (Transition, Place) {}
    Association PortTransition (Port, Transition) {}
    Association PortPlace (Port, Place) {}
}