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From: lindsay@comp.vuw.ac.nz (Lindsay Groves)
Newsgroups: comp.ai,sci.philosophy.tech,talk.philosophy.misc
Subject: Re: Is Computer Science Science?
Message-ID: <12999@comp.vuw.ac.nz>
Date: Tue, 29-Sep-87 22:08:00 EDT
Article-I.D.: comp.12999
Posted: Tue Sep 29 22:08:00 1987
Date-Received: Sat, 3-Oct-87 08:22:07 EDT
References: <5113@sunybcs.UUCP> <6195@apple.UUCP> <5068@jade.BERKELEY.EDU>
Reply-To: lindsay@vuwcomp.UUCP (Lindsay Groves)
Distribution: world
Organization: Comp Sci, Victoria Univ, Wellington, New Zealand
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Xref: mnetor comp.ai:827 sci.philosophy.tech:496 talk.philosophy.misc:722

In article <5068@jade.BERKELEY.EDU> ed298-ak@violet.berkeley.edu (Edouard Lagache) writes:
>>>
>.... Does Computer Science have any laws?
>>>
>>"Anything that can go wrong will go wrong."
>> ...
>
>	Hey those aren't laws from Computer Science, they are from the 
>	Science (Religion?) of Murphyology.!
>
>								E.L.

The August issue of the Communications of the ACM contains an article by
C.A.R.Hoare and eight others, entitled "Laws of Programming".  One of their
laws (4) is:
		ABORT U P = ABORT
where ABORT (which they denote by an upside down T) is a statement that can 
do anything ("It places no constraint on the executing machine, which may do 
anything, or fail to do anything; in particular, it may fail to terminate"), 
and U is nondeterministic choice.

The text explaining this law says:
  "This law is sometimes known as Murphy's Law, which state, "If it can go 
  wrong it will"; the left-hand side describes a machine that CAN go wrong
  (or can behave like P), whereas the right-hand side might be taken to
  describe a machine that WILL go wrong.  But the true meaning of the law
  is actually worse than this: The program ABORT will not always go wrong --
  only when it ismost disastrous for it to do so!  THe abundance of empirical
  evidence for law (4) suggests that it should be taken as the first law of 
  computer programming."

It seems that being part of "Murphyology" doesn't preclude something from
being a law of Computer Science -- this one is given a very precise
statement and interpretation as a law of programming, which must also count
as a law of Computer Science.  Given that Computer Science draws heavily on
such fields as mathematics, logic, linguistics (Chomsky's hierarchy has far
more relevance to Computer Science than it does to lingusitics!), electrical
engineering etc., it is not surprising that laws in Computer Science should
bear similarity to laws in other areas.

	Lindsay Groves
	Logic programmers' theme song: "The first cut is the deepest"