Behavioural approaches to algebraic specifications

This paper focuses on observability issues in the framework of loose algebraic specifications. The main purpose of observability is to extend the model class of some given algebraic specification in order to consider not only the algebras that satisfy the axioms of the specification in order to consider not only the algebras that satisfy the axioms of the specification, but as well other ones, provided that the differences between the properties satisfied by these algebras and the properties required by the specification (i.e., the axioms) are not “observable”. We compare various behavioural approaches developed so far. We point out their respective advantages and limitations. Expressive power is our main criterion for the discussion.