Examples of program composition illustrating the use of universal properties

This paper uses a theory of composition based on existential and universal properties. Universal properties are useful to describe components interactions through shared variables. However, some universal properties do not appear directly in components specifications and they must be constructed to prove the composed system. Coming up with such universal properties often requires creativity. The paper shows through two examples how this construction can be achieved. The principle used is first presented with a toy example and then applied to a more substantial problem