Is there a description of Prolog language (syntax and semantics) available online?
There are a lot of reference manuals for implementations. But neither of those is a language description. For example the SWI Prolog manual states
This manual does not describe the full syntax and semantics of Prolog.
And refers to a set of books printed on paper, published in the nineteen eighties. And to ISO standard which is for money and "should be available from my country's ISO representative" gibberish.
The ISO standard is available for a very low price (currently USD 30 60) from the ANSI webstore as an INCITS document. There you also get the two corrigenda for free. See iso-prolog tag info for all current documents. Here is a comprehensive overview of all built-in predicates which includes Cor.1 and Cor.2.
If you want a printout version, the best is still to print above INCITS document yourself being aware that page 10 is missing (a page left intentionally blank) — otherwise odd pages are on the left side. The document is an A4 scan with two columns per page. The informal Annex A goes better in a separate binding. Instead, add the two corrigenda!
Alternatively, SAI sells hardcopies.
You might want to use the following preprint of an
appendix of a book that is not the ISO core standard:
ISO Prolog: A Summary of the Draft Proposed Standard.
Michael A. Covington, 1993
http://www.uv.es/fbarber/prolog/isoprolog94_ps.Z
http://www.dropbox.com/s/kr1pbrfc1kqzdpq/isoprolog94_ps.Z
It is much shorter than the full ISO standard, but
it informally predates and covers almost the same.
来源：https://stackoverflow.com/questions/10914155/a-searchable-prolog-language-description-online