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From: orville@weyrich.UUCP (Orville R. Weyrich)
Newsgroups: comp.software-eng
Subject: Re: Modifiability
Message-ID: <1991Jun7.165928.1903@weyrich.UUCP>
Date: 7 Jun 91 16:59:28 GMT
References: <1991Jun5.201807.13286@netcom.COM> <62683@siemens.siemens.com> <11714@ncar.ucar.edu>
Reply-To: orville@weyrich.UUCP (Orville R. Weyrich)
Distribution: comp.software-eng
Organization: Weyrich Computer Consulting
Lines: 47

In article <11714@ncar.ucar.edu> ftower@ncar.ucar.EDU (Francis Tower) writes:
>In general, the traditional waterfall life-cycle fails when maintenance is
>concerned because those fine, fat documents which tell managers that a phase of
>the development is finished are left to gather dust.  In particular the
>software specification is often never revised  and the product begins to
>diverge from the specification.  The result is that the source itself is
>maintained and both old and new optimization knowledge is spread into the
>source with details lost.

I agree.

>Balzer, Cheatham and Green in their classic paper 'Software Technology in the
>1990's: Using a New Paradigm' (IEEE Comp. Nov 1983)  proposed that a program's
>specification be formalized and that the implementation be mostly automated. 
>The problem then of maintainability would be pushed into the specification
>phase.

The problem with this is that the specification becomes to all intents and
purposes the programming language, and if Ada or C (or something else) is
later generated automatically from this specification, its just an intermediate
pass of a huge compiler.

In effect, the specification language becomes the language in which the 
source code is written.

What are the implications then of Balzer et al's paper?

1) Source languages should be more formal so that more consistency checking
   can be done. [There has been some movement in this direction. Eiffel for
   example allows assertions as part of the language. SETL provides a formal
   framework. IMHO there is progress, but a long way to go. It is not
   clear to me that many of today's programmers are willing or able to go 
   the distance here.]

2) The amount of work done prior to beginning coding should be minimized.
   [At first blush, this is contrary to conventional wisdom. But it is not
   really, if the coding environment supports stepwise refinement and 
   consistency checks along the way. Consider the use of Ada as a PDL as
   movement in this direction.]
   

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Orville R. Weyrich, Jr., Ph.D.                   Certified Systems Professional
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