Dear Al Vilcius, Yes, I have done some work along the lines that you query, using theories and models from hidden sorted equational logic to explicate classes and objects. You can find details in @incollection(tpasth, title = "Types as Theories", author = "Joseph Goguen", booktitle = "Topology and Category Theory in Computer Science", editor = "George Michael Reed and Andrew William Roscoe and Ralph F. Wachter", publisher = "Oxford", year = 1991, pages = "357--390", note = "Proceeding of a Conference held at Oxford, June 1989") As a general orienting remark (pun intended), existing languages tend to have been designed from an ad hoc, partial instantiation of the relevant concepts. For example, C++ was constrained to be an extension of C, and hence inherits all of its faults and limitations, with the result that it cannot realise the full potential of the object paradigm. Also, I do not quite agree with all of the definitions that you quote. In particular, it is significant that "objects" have actual dedicated local storage; hence, they are not just software; they are run-time entities. And "polymorphism" as usually understood in computing has to do with overloading operations; perhaps this is intended to be a reference to what is usually called "dynamic binding"? If so, it is unnecessarily oblique and obscure. The definition of "data abstraction" is not much better. Yours, Joseph Goguen &&&&&&&&&&&&&&&&&&&&&&&&&&&&& Signature File &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& Joseph A. Goguen, Professor of Computing Science, Programming Research Group, University of Oxford, 11 Keble Road, Oxford OX1 3QD, United Kingdom. email: Joseph.Goguen@prg.ox.ac.uk [internet] -- usually also works in the UK, but if not, try Joseph.Goguen@uk.ac.ox.prg phone: 272567 [my office]; 272568 [secy]; 273838 [PRG office]; 273839 or 272582 [FAX]. From USA, dial 011-44-865-...; from UK, dial (0865)-... ============================================================================== 1aug92-1jan93, sabbatical: Technical University of Nova Scotia School of Computer Science P.O.Box 1000, Halifax, Nova Scotia, Canada B3J 2X4 phone: (902)420-7776 [direct]; (902)420-7718 [sec]; (902)420-7858 [fax] email: goguenja@newton.ccs.tuns.ca [email to goguen@prg.ox.ac.uk should also be forwarded] Our home address is: 5742 Victoria Rd, Halifax, Nova Scotia B3H 1N2 Canada phone: (902)422-1361 ==============================================================================