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

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