🚀 go-pugleaf

In article <249@gould.doc.ic.ac.uk>, cdsm@ivax.doc.ic.ac.uk (Chris Moss) writes:
> I presumed that you meant something far more specific than that.
> I doubt anyone could deny that our work is based on Edinburgh Prolog
> as described in Clocksin & Mellish.
> Most of the discussions on this net are about details that C&M do NOT
> cover--maybe that's part of the problem.

The BSI group have felt free to change things that C&M *did* describe clearly.
The phrase "as described in" is perhaps ambiguous.
Reading 1:
	"Edinburgh Prolog (that is, exactly what is in Clocksin & Mellish)".
Reading 2:
	"Edinburgh Prolog (that is, the dialects that Clocksin & Mellish
	refer to and partly describe)".
Since C&M is far too vague about details to serve as the basis for a standard,
I find reading 2 the most plausible one.

It is very easy to deny that the early work was based on Edinburgh Prolog:
some of the early stuff looked uncommonly like Sigma Prolog.  Indeed,
document PS/69 (dated 6 June 1985) explicitly says that the standard was
now to be based on micro-PROLOG as well as C&M.

> >%	Note that it says clearly:
> >%	(a)  No research and development work either in progress or yet
> >%	     to be started will be depended on.  At the time, I took this
> >%	     to promise that they would be trying to standardise practice
> >%	     as it stood in January 1985, not to invent a new language.
> >%	(b)  The CONTENT of the standard is to be based on Edinburgh
> >%	     Prolog, as described in Clocksin & Mellish.  At the time, I
> >%	     was so naive that I took this to mean that the standard was
> >%	     to be based on Edinburgh Prolog.
> 
> Do we not allow anything not stated in the C&M "de facto standard"?
Consider, for example, the phrase "the English language, as described by
Jespersen".  Would anyone take this to mean _only_ what Jespersen described?
No, this would be taken as a pointer to Modern English, as distinct from
Black English, Middle English, or Pidgin English.  And since Jespersen
described both English and American, it would be taken to refer to both
those dialects.

Similarly, by Reading 2, one would take "Edinburgh Prolog, as described
by Clocksin & Mellish" to refer to the dialects C & M were concerned
with but did not fully describe, namely DEC-10 Prolog, EMAS Prolog (C
Prolog's immediate ancestor), and PDP-11 Prolog.  Given their close
relationship to PDP-11 Prolog, and their close relationships to Clocksin
and to Mellish, it would be reasonable to count ESI Prolog 1 and PopLog
as "Edinburgh Prolog" within the meaning of the act.  But it is clear
that IC-Prolog, micro-PROLOG, Sigma Prolog, LM-PROLOG, and Waterloo
Prolog, despite their virtues, are _not_ "Edinburgh Prolog" within the
meaning of the act.

> There is all the difference in the world between basing something on
> a proposal and adopting that proposal lock stock and barrel.
Indeed there is.  There is also all the difference in the world between
basing something on the dialects referred to in a book and going off and
inventing your own.

> If it had been stated that it was based on MProlog or Marseille Prolog
> or microProlog it would look an awful lot more different to what it 
> looks like now.

I'm not sure that I believe this:  there was a serious proposal early on
to base BSI standard syntax on that of Sigma-Prolog, which is an immediate
descendant of micro-PROLOG, and as pointed out above, PS/69 _did_ say in
June 85 that (contra the January 1985 promise) the stanard _would_ be
based on micro-PROLOG _as well as_ Clocksin & Mellish.  (Which is rather
like basing a standard on BASIC as well as FORTRAN.)

> Rereading
> >%    At the time, I took this
> >%	     to promise that they would be trying to standardise practice
> >%	     as it stood in January 1985, not to invent a new language.
> 
> I realise that this is partially at least a retraction of what
> Richard had said.

You realise wrong.  It is not a retraction of anything at all.
It is a simple statement of what, in 1985, I took the text to mean.
While it may not be what the author intended, I _still_ think that's
how the _text_ is most naturally interpreted.

> The submission certainly did NOT say that it would
> take no account of current research,

Neither did I say that it did.  But it DOES say quite explicitly that
no additional research beyond what had already been done by January 1985
would be REQUIRED to complete the standard.


ERRATA:
    I had forgotten about document PS/45 by Roger Scowen, entitled
	"A standard Prolog - A tentative proposal, draft".
    This is a 2-page draft dated 24 May 1985.  However, it does not
    count as the first draft promised for the end of 1985--it is little
    more than a list of which predicates might be in the standard.

    I would argue that PS/45 clarifies how "based on Edinburgh Prolog..."
    is to be interpreted, because it includes predicates which are not
    described in Clocksin & Mellish, but _are_ in some of the dialects
    I take that phrase to identify.