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From: mmh@cs.qmw.ac.uk (Matthew Huntbach)
Newsgroups: comp.lang.prolog
Subject: Re: Need debugging reference
Message-ID: <3275@sequent.cs.qmw.ac.uk>
Date: 22 Jan 91 11:10:42 GMT
References: <1991Jan21.230001.12890@csn.org>
Organization: Computer Science Dept, QMW, University of London, UK.
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In article <1991Jan21.230001.12890@csn.org> citrin@csn.org (Wayne V. Citrin) writes:
>Which paper first proposed the common Prolog debugging paradigm (procedures
>as 'boxes', and each box having four 'ports': CALL, EXIT, REDO, and FAIL)
>that most Prolog systems offer?
>
I think the following is the earliest reference:

[Byrd 80].
  L.Byrd.
  Understanding the control flow of Prolog programs.
  In Proc. Logic Programming Workshop 1980,
  Debrecen, Hungary ed. S-A.Tarnlund.

Hence the boxes are sometimes referred to as "Byrd boxes".

Matthew Huntbach