Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!ubvax!vsi1!altnet!uunet!mcvax!ukc!mupsy!mucs!ralf
From: ralf@mucs.UX.CS.MAN.AC.UK (Ralf Kneuper)
Newsgroups: comp.software-eng
Subject: Re: Design Methods and Flow charts
Message-ID: <4471@mucs.UX.CS.MAN.AC.UK>
Date: 28 Jul 88 16:56:54 GMT
References: <1440@bute.tcom.stc.co.uk> <2672@newton.praxis.co.uk> <382@gould.doc.ic.ac.uk>
Reply-To: ralf@mucs.UUCP (Ralf Kneuper)
Organization: Computer Science, University of Manchester, UK
Lines: 36

In article <382@gould.doc.ic.ac.uk> acwf@doc.ic.ac.uk (Anthony Finkelstein) writes:
>Simon Tait in article <2672@newton.praxis.co.uk> writes that JSP and
>OOD are normally termed semi-formal methods. This is the normal usage
>but is inaccurate - something is either formal or not! I prefer to
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>use the term formatted to describe such methods - it more accurately
>captures the essence of the representation schemes associated with
>such techniques. Pedants rule OK!
>
>Anthony Finkelstein

Sorry, but there can be no method that is 100 percent formal, formality is a
question of degree. The problem is that if you want to be formal, you have
to use a language and method with formally defined semantics, The language
for describing these has to be defined formally itself, etc. - you never
get to the bottom of it. At some stage you just have to say "Ok, I *know*
what this means and I am not going to take formalization any further". In
some way, this is similar to axiomatization in  mathematics.
When defining the semantics of something you always have to use some
language for describing them and just assume that you know what its
constructs mean. The difference between informal, semi-formal and formal
methods then lies in how far you take this process - do you explain what
the various objects of your method mean in terms of natural language plus
pretty pictures, in terms of mathematics (in particular mathematical
logic), or do you stop somewhere in between?

If you are interested, this was put rather strongly by Naur (Formalization
in Program Development, BIT 22, 1982, pp 437-453), but he then went over
the top and claimed that formal methods are no use since you cannot be
completely formal. 

Ralf
-- 
 Ralf Kneuper, Dept of Computer Science, The University, Oxford Road,
 Manchester M13 9PL, UNITED KINGDOM.    
 UUCP:  uunet!mcvax!ukc!man.cs.ux!ralf | Tel:   (+44) 61-275 2000 Ext 6134 
 JANET: ralf@uk.ac.man.cs.ux