Supported relations
// Directed relations
A.b -> B;
A.b? -> B;
A.bs* -> B;
B <- A.b ;
B <- A.b? ;
B <- A.bs*;
// Bidirectional relations
A.b <-> B.a;
A.b <-> B.a?;
A.b <-> B.as*;
A.b? <-> B.a;
A.b? <-> B.a?;
A.b? <-> B.as*;
A.bs* <-> B.a;
A.bs* <-> B.a?;
A.bs* <-> B.as*;