GNU Prolog language syntax specification

[Randall Landau]

Hello.

I'm trying to track down a description of GNU Prolog's syntax, and for
the life of me I cannot find it anywhere.

Specifically, I'm looking for an abstract description in BNF form,
that you would use, for example, to write a parser for a programming
language.

I've looked in the source code, but didn't see anything that screamed
out at me "THIS IS IT!," and I figure it would be easier to find it
elsewhere, than reconstruct it from the source code.

Searching with Google comes back with numerous examples of defining
other languages in prolog using BNF, but not the BNF for prolog
itself.

Looking through the GNU Prolog documentation doesn't turn anything up.

Searching the mailing list archives, I find 1 message, where someone
asked the same question 5 years ago, and the best response he got was
to buy a book for $80 that has a chapter on a fragment of the
language.

Surely this information exists somewhere. Can someone point me in the
right direction?