We can make these attributes of a circle, but that masks the fact that any one of them is calculable from any other. They are strongly associated. We have the numeric structure connecting their numeric value attributes, but can we know something about the association without searching through numeric structure?

 We can’t link Radius and Diameter through a true ISS operator – they are not synonyms – but they are strongly related. We could use a partially true ISS operator – an association which needs to be discovered. That is, a not exactly true synonym.

 When we search on the parents of the instantiated radius, we find circle radius, then move to diameter, find an inherited value. We convert diameter into radius, compare the inherited value with the actual value, and return an error.

 The same mechanism would apply if the attributes were related in any other way – say through a relation that would permit one attribute to be discovered from another, or from several others.