wrong sig object get referenced to while executing state in Alloy

Question

I am new to Alloy. I am trying to formalize a system using Alloy. Here I want to execute certain operations based on the events. For this, I have a list of events that I want to track using enum Event. And I am going through all the State using ordering function of Alloy. In each state, I am taking the mixture object and running the operation.

Problem that I am facing currently is - In my system, I have two sig object - ClassA and ClassB. After executing the alloy code I am generating the flow diagram. Unfortunately, I am noticing my ClassB get referenced to ClassA of Mixture object. I am attaching the diagram

I am also attaching my full code here. Can anyone help me debugging the problem, please? I have tried to impose different predicate and logic, but none of them worked.

open util/ordering[State]


abstract sig Base{
 name: String,
 value : Int
}{
value >= 0
}

sig ClassA extends Base{

}{

name = "Class A"
}

sig ClassB extends Base{


}{
name = "Class B"
}

enum Event {EVENT1, EVENT2}


sig State{

mixture: Mixture
}

sig Mixture{
classA: Base,
classB: Base
} {
    classA != classB
}


fact {
    all s: State, s': s.next{
        s.mixture ! in  s'.*next.mixture
        operation [s.mixture]       

    }
}


pred operation [mixture: Mixture]{
    all ev: Event| ev = EVENT1 => {
        mixture.classA.name = "Class A" => {
                mixture.classA.value = 1    
        }
    }

}

run random {} for 3

Answer 1

You have

sig Mixture{
classA: Base,
classB: Base
}

In your diagram, the relations are named classA and classB . Since each can point to any arbitrary Base , there's nothing stopping classA from pointing to a ClassB instance. You probably want something like

sig Mixture {
    , classA: ClassA
    , classB: ClassB
}