Comments on "A formal semantics for object model diagrams"

The author indicates some things that need clarifying in the paper cited in the title. The paper does not make it clear that a class of objects is not equivalent to a set of tuples. In a set of tuples two different tuples cannot contain the same data. Two different objects in a given class can contain the same data. In most of the paper this does not matter. However, the simulation function between a subclass and a superclass must be injective, but the (overloaded) simulation function between the sets of tuples usually cannot be injective.