Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!ukc!mucs!cliff From: cliff@cs.man.ac.uk (Cliff Jones) Newsgroups: comp.specification Subject: Re: Difference between Spec and Code? Message-ID: <1889@m1.cs.man.ac.uk> Date: 6 Nov 90 15:49:25 GMT References: <13576@june.cs.washington.edu> <1990Oct31.102351.21789@newcastle.ac.uk> Sender: news@cs.man.ac.uk Reply-To: cliff@cs.man.ac.uk (Cliff Jones) Organization: Department of Computer Science, University of Manchester UK Lines: 21 In article <1990Oct31.102351.21789@newcastle.ac.uk> des0mpw@colman.newcastle.ac.uk (M.P. Ward) writes: >I always used to say "a specification is more abstract than a program" >(there is a continuum here ranging from "low-level" programs to "highly >abstract" specifications - its not an either-or relation). Then I was >challenged to define what I meant by "more abstract". The best definition >I could come up with was SMALLER (and more readable - but the metric >which coresponds most closely to intuitive notions of readablility is size!). I have used the argument of size myself but I think it is less important than the tractability of the specification languages we should like to see used. It is - for example - true that a specification in terms of objects like sets and maps is shorter than one in terms of bytes/pointers but the key issue is that one can reason about the mathematical objects precisely because they have evolved to systems with sets of operators with nice algebraic properties. BTW I still stand by the *technical* arguments given in the paper by Hayes/Jones referred to earlier in this news group. cliff jones