🚀 go-pugleaf

Newsgroups: comp.lang.prolog
Subject: Re: BSI Prolog terms of reference
Summary: 
Expires: 
References: <831@cresswell.quintus.UUCP> <249@gould.doc.ic.ac.uk> <256@gould.doc.ic.ac.uk> <883@cresswell.quintus.UUCP> <273@gould.doc.ic.ac.uk> <386@aiva.ed.ac.uk>
Sender: 
Reply-To: cdsm@doc.ic.ac.uk (Chris Moss)
Followup-To: 
Distribution: 
Organization: Dept. of Computing, Imperial College, London, UK.
Keywords: misdirection, misunderstanding, standards

In article <386@aiva.ed.ac.uk> jeff@uk.ac.ed.aiva (Jeff Dalton,E26 SB x206E,,2295119) writes:
>It is, I think, at least misdirection to answer Richard by saying
...deleted for space reasons
>These things may all be true, but by "misdirection", I mean a
>reminder that Richard has raised some issues that deserve a direct
>answer.  Just because Richard might be inclined towards Edinburgh
>Prolog in any case doesn't mean he isn't right when he says the BSI
>proposals go too far beyond codifying current practice or that users
>will find the cost of conversion too high.

First of all let me thank you for trying to say things clearly and
dispassionately and with references. If I've overreacted, I'm sorry.

I thoroughly agree that Richard has raised a lot of points that need
answers. Some I've tried to answer; others I will attempt to answer
in future as I clarify the issues with other members of the committee.

>... there are times when you seem to be muddying the waters
>rather than responding fairly to what Richard said.  I am not saying
>that is your intention, but it is sometimes what happens.
>
>For example, here is the exchange that began the issue of
>"personalities":
>
>In article <845@cresswell.quintus.UUCP> ok@quintus.UUCP (Richard A.
>O'Keefe) wrote:
>- 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.
>
>In <256@gould.doc.ic.ac.uk>, you quoted Richard's remark and replied:
>+ I work in the same establishment as the authors of SigmaProlog.
>+ I'm not going to start badmouthing them on the net.
>
>I don't see anything in the passage you quoted that amounts to
>badmouthing the authors of Sigma Prolog -- or did you mean that
>*you* weren't going to badmouth them because you worked in the
>same place?  

Yes, that  is precisely what I _said_ (i.e. *I* didn't want to do the
badmouthing). I never suggested that Richard was doing any
badmouthing and I'm sorry if people took that implication. It seemed
to me that Richard was criticizing the introduction of any ideas that
arise from sigmaProlog and wanting the committee to disassociate
themselves totally from those ideas.  I found it hard to believe
that, knowing that Frank McCabe was involved in the standardization
process (he quoted him at the Boston conference saying there'd be a
standard within a year), he should be surprised that he would want to
introduce ideas drawn from that dialect of Prolog. 


>Richard was responding to an earlier claim that it was hard to deny
>the work was based on Edinburgh Prolog.  Specifically, in
><249@gould.doc.ic.ac.uk>, you said:
>
>   I doubt anyone could deny that our work is based on Edinburgh
>   Prolog as described in Clocksin & Mellish. But should it be
>   limited precisely to that?
>
>The actual disagreement seems to be that Richard had in mind "based on
>E.P. alone" while you had in mind "based on E.P. and other Prologs".
>Richard brought in PS/69 to give some concrete backing to his "looked
>uncommonly like", so that it would be clear that his remark was not
>based on a mere impression.

If Richard had in mind "based on E.P. alone" then why didn't he say
it? His original statement (to quote it once more) was:
  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.  

Maybe I should mentally have inserted the word "alone" into that
sentence but I didn't, and I don't think that's altogether my fault.

Let me quote the section from PS/69 for those who haven't seen it:

   Which Prolog implementation should form the basis for a standard?

  Adopted: (8) Include features described in both Clocksin & Mellish
  and Clark & McCabe, judge other features on their merits.

(i.e. it was the book in both cases not the implementation that was
cited. I'm not suggesting this is very significant, but up to 1985
they were probably the most widely circulated Prolog books.)

Now the resolution is in itself a thoroughly confusing statement. It
seems to say that one takes the common subset of C&M and C&McC. This would
involve ignoring nearly everything in both books say about syntax,
built-in predicates, etc. It was presumably supposed to mean the union. 

Having taken that decision, the strategy of providing two syntaxes
united by a common semantics was, I suggest, the right one. Thus
there was an Edinburgh-based syntax and a micro/sigma based syntax.
What Richard was criticizing was the current version of the
Edinburgh-based syntax. Thus his objection that it was affected by
sigma is mysterious to me. We haven't tried to make Edinburgh look
like sigma or vice-versa (it would be totally impossible anyway).
We've tried to keep a multiplicity of syntaxes.

Thus I assumed that Richard and others accepted this twin-track
policy. If they don't maybe we should go back and discuss where the
problem is. Is it simply an unworkable ideal, or is it (as I suspect)
that he feels that the BSI committee was bound to keep only to
Edinburgh and was therefore betraying its principles by being
pluralist?

Where the strategy has run into serious problems is, I would suggest, at
the level of built-in-predicates. Though in many cases it's just a naming
question, there are differences which are hard to ignore semantically:
e.g. what happens to read and get at the end of file.  I doubt the people
defining these have consciously followed sigma/micro any more than
Edinburgh, but it has doubtless contributed to the muddle.

Underlying this whole discussion is, effectively, the issue of the market
penetration of "Edinburgh" Prologs. I will agree that there is a
substantial core of unity which is much greater than that represented by
the current BSI proposals. Unfortunately most of it is documented 
inadequately in reference manuals. The best account is still Richard's
document known as PS/6, which is now being used much more in constructing
the BIP definitions. (But that would take us into a methodology discussion
which I want to avoid here.)

>Another example is the following:
>
>In article <845@cresswell.quintus.UUCP> ok@quintus.UUCP (Richard A. O'Keefe) writes:
>- 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.
>
>In <256@gould.doc.ic.ac.uk>, you replied:
>+ I don't find Reading 2 any more plausible than my original.
>
>+ "Clocksin and Mellish were trying to describe what was going on at
>+ Edinburgh. Therefore one takes not what they said but what they were
>+ trying to say, which is obviously...  (insert one's own prejudice)"
>
>There is certainly an argument to be made here, namely that the
>pahrase cannot be clarified as easily as Richard suggests.  But
>your rephrasing of Reading 2 is hardly a fair one.  It is not just
>a question of one prejudice verses another: there are facts involved,
>and Richard is an expert on those facts.  Nor is it right to say
>Clocksin and Mellish were "trying to describe what was going on
>at Edinburgh".  They described a "core Prolog".

I was simply trying to make the point that what there was was
informal and unclearly defined. My use of the word "prejudice" was
unfortunate: I was not casting aspercions at Richard or anyone.

Sure, C&M were trying to describe a "core Prolog", (I don't see that
my more graphic description is misleading) but it is precisely the
umbra round the core that causes many of the problems.

Part of the problem in the BSI committee is probably that very few of
the actual committee regularly used an Edinburgh Prolog. To name a
few used by the active members, there were microProlog, Salford
Prolog, Poplog, ESI Prolog 1 & 2, ICL Prolog, VM Prolog and more recently
CRISS Prolog, Prolog II, BIM Prolog, ZYX Prolog. Very few of these
are in the "Edinburgh family". The only subcommittee actually to meet
in Edinburgh regularly (modules) dissolved itself a year ago after
coming to no agreement.

The underlying reason for this is that standardisation is a very
boring activity. One ends up having the same discussions and
arguments again and again. Most such committees only work by having
one or two dynamic leaders who drag everyone else along. The BSI
committee hasn't had such people who are prepared to give their time,
except Richard at the beginning, as I have said before. 

Standards are things that are drafted on paper, not decisions that are
taken at committee meetings. There were quite a few prepared to come to
the meetings and argue, but not to commit themselves to paper. (For
instance, Chris Mellish and Bill Clocksin both had more important
commitments which prevented them doing more than attending main meetings.
I regret very much that they seem to have dropped out altogether now
though I can't say I blame them.)

>Finally, there is the question of the correspondence between Richard's
>position and the interest of Quintus.
>
>> I wrote:
>>   I don't object to you arguing for the standard to be based on Quintus.
>>   You might be considered to be failing your employers if you didn't.
>
>The point is that Richard *wasn't* arguing for a standard to be
>based on *Quintus* Prolog.  Edinburgh Prolog is not the same thing
>as Quintus Prolog.  That Richard is arguing for a standard based on
>Quintus is simply false regardless of his motives.

And if you look at my statement, you'll discover that my statement
also does not presuppose that he is arguing for Quintus. Ok it's
ambiguous, but what I actually MEANT was
  "Richard I would not object if you DID argue for the standard to be
based on Quintus".

I hope you will agree that that is a permissible reading of the
sentence, even if not the most likely.

I have not at any time thought that Richard was acting partially. I did
not intend to imply that he was. I am sorry that people took it that way.
I suppose the problem was that it never occurred to me that either he or
anyone else would think for a moment that he WAS acting partially (in
respect of Quintus, that is). Maybe one of the problems of USENET is that
one is typing away in what feels like a private conversation--but it
isn't.

Chris Moss.