Project "Contraintes" Prolog Web Pages: The ISO Standard
The ISO Prolog standard: ISO/IEC 13211-1 was
published in 1995.
Work on the standard began in Britain in late 1984.
In 1985 AFNOR formed a Prolog group, which worked in cooperation with the British group.
Only in 1987 was the ISO/IEC JTC1/SC22
group WG17 created.
The original intention of the standards process was, in so far as might be possible, to
standardize the existing practices of the many implmentations of Prolog.
Prolog, was (is) after all
a simple and logical language.
The events were hovwever to reveal not only many variations in practice but also a number of
significant areas where the internals of the language proved to be poorly understood.
Areas where the standard clarifies aspects that were previously abmiguous
New departures in the standard
- Not wishing to part with the convention that a standard should break as many implementations as possible
the standard introduced an IO system which departs
radically from the " see " and " tell " predicates of
- In a different direction and following principles from software engineering
the standard introduced control constructs for
Work in progress
In the interests of creating a standard before the expiry of the millenium,
the questions of modules and grammars both
features of many Prologs were put off into a second part of the standard. This part subsequently concentrated on the setting of standards for Prolog modules and should appear by early 2000. Grammars are thus not (at present) part of ISO
Prolog, nor arethey expected to be in the near future.
Tests of Standard conformance
As a service to implementors and others wishing to test compliance of a given
Prolog implementation with part I of the standard the following links provide
tests that can be used to verfiy compliance.
Author: J.P.E. Hodgson
Saint Joseph's University
Philadelphia PA 19131
Last Changed: 1 March 1999