| Thanks for trying to correct me, if I'm wrong (but thanks anyway). What I write
is the impression I've formed after reading various sources on the history of
Prolog, over the years. Some of them are even by Kowalski himself and my
impression that he was the "neat" and Colmerauer the "scruffy" comes from his
comments on their relation. I certainly could have misunderstood his comments,
or be misremembering them. Unfortunately it will take me some time to dig out
the specific sources and check my assumptions [1]. One such recent source is this documentary (in French) about Alain Colmerauer by
a lady who shares his surname (a relative, I'm guessing): https://youtu.be/74Ig_QKndvE?t=311 I've pointed the link to just before the start of an interview with Kowalski
where he says (in English) what I transfer above, that Colmerauer was more
practically minded and coming from a computer science side point of view while
he (Kowalski) was more theoretically minded and coming from a mathematical logic
point of view, and also that this tension created an "alchemy" that would not
have transpired otherwise. I watched this documentary very recently and I guess
it coloured my comment above. More generally, it's easy to find discussion of the "pure" subset of Prolog and
about its purported advantages compared to the rest. I'd have to go back to
those textbooks to be sure, but I think I first encountered this idea in The
Art of Prolog (O'Keefe) or "The Craft of Prolog" (Sterling & Shapiro), or
probably both. And I have heard Ivan Bratko's coding style in his Prolog
Programming for AI described as being too imperative and not the recommended
style today [2]. I guess what people mean when they talk about "purity" is the lack of
side-effects, and other concessions to the everyday needs of the working
programmer. I understand the occurs-check flag to be one such concession, for
example [3]. So I don't think that all this is just my imagination. In my experience, there
really is a divide between Prolog users that think of Prolog as a kind of
mathematical notation for computers and smart at the thought of its "dirty"
side-effects, and those who just want to use it as a powerful, and beautiful,
tool. Like myself. But I should try to be less sentimental in my analysis in the future. Again,
thanks for reminding me to check my assumptions and try to remember where my
knowledge comes from. _____________ [1] I spent four years during my PhD at Imperial College literally down the
corridor from Kowalski's office, but I never had the guts to go and talk to him
and ask him about Prolog's history, that I am always very curious about. I
regert that now that my PhD is ended and I'm no longer in the same building, or
the same city :/ [2] Which is nonsense. Also Bratko said I'm good with Prolog, so there. [3] What does the DEC10 Prolog manual say about the occurs check? |
See I.2.1. Occur Check of https://userweb.fct.unl.pt/~lmp/publications/online-papers/D...
A recent related discussion: https://stackoverflow.com/questions/65600226/what-occurs-che...
In general, we do agree on the observation that Prolog profits from both the theoretical and the practical side. But still even today I have the impression that the highly theoretically leaning side does not appreciate the fundamental contribution errors have on ensuring correctness properties. At least this was my impression of November 10th in Paris.
Just one personal recollection (from memory) which probably also influences my view on the Kowalski-Colmerauer relation. At a META 90 tutorial/talk about meta interpreters, Sterling attributed the origin of meta interpreters to Warren and the DEC10 manual. Kowalski responded (publicly during the talk) that this was well known to Colmerauer, well before Warren ever got into Prolog.
As to the lady you are referring to she is his widow, a linguist.