Supporting the evolution of class definitions

Barbara Staudt Lerner of University of Massachusetts at Amhearst (USA) spoke on “Extending the Notion of Type Conformance to Interfaces and Type Systems.” This is work pursued in the context of interface type hierarchies which are independent of their implementation class hierarchies. This was work in progress which seeks to extend existing type systems to allow existing instances to evolve to new implementations of classes. She makes the observation that existing types rarely delete functionality. This is the case to optimize. Types which delete functionality are not as important, since it is nearly impossible to support in any meaningful way.