Alloy Term to get all Subsig

Question

Is there a way to express that all objects of Sig2 are either related by a rel relation to elements of Sig1 or are subsigs? I want something like either_rel_or_subsig but the code might be extended and someone else might introduce SubSigC. Then, either_rel_or_subsig would forbid any SubSigC object.

module test

sig Sig1 {}

sig Sig2 {
  rel: lone Sig1    
}

sig SubSigA extends Sig2 {}
sig SubSigB extends Sig2 {}

fact either_rel_or_subsig{Sig2 in rel.Sig1 + SubSigA + SubSigB}

run {}

question from:https://stackoverflow.com/questions/66054570/alloy-term-to-get-all-subsig

Answer 1

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