10. Behavioral refinement:
This chapter extends the notion of types
as constraints to include behavioral properties.
It presents an assertion logic for the verification
of programs and discusses the operational
model underlying the verification of object behavior
based on traces.
It further gives precise guidelines to
determine whether classes that are syntactical subtypes
satisfy the behavioral refinement relation.
Finally, an overview is given of formal approaches
to characterize the behavior of collections of objects.