ISO/IEC JTC1 SC22 WG17 Minutes
Date of meeting: June 7th 2021
Time of meeting: 17:00 - 18:06 UTC

1. Greeting and introduction of participants, administrativa

Bill Ash (ISO)
Klaus Däßler (Germany)
Manuel Hermenegildo (Spain)
Stefan Kral (Austria)
Per Mildner (Sweden)
Ulrich Neumerkel (convener)
Francisco Morales (Spain)
Mark Thom (Canada)
Markus Triska (Austria)

Ad 1.1 Minutes of 2020 meeting N282 were approved.

Agenda item 3 was discussed first.

Ad 3. DCG progress.  DCGs cannot be issued as a TR, need to be issues as
TS to permit normative language in the document.

Resolution:

WG17 asks UN to prepare an NWIP for a TS of DCGs with UN as project
editor and a 36 month timeframe.

Unanimous

Ad 1.2 Recent progress in Prolog systems

Two new implementations (Scryer, Trealla) have chosen to support an
additional transparent representation for lists of characters using a
compact (byte wise) UTF-8 encoding while still being fully unifiable
with lists and lists of characters.  This reduces the representation of
text as lists of characters by a factor of 16 to 24 while maintaing
full conformance requiring no extension to 13211-1.  Scryer also
supports partial strings.

http://github.com/mthom/scryer-prolog/issues/95

Other discussion was about clause indexing techniques, general
performance guarantees, variable ordering, modules and Unicode support
in current systems.

There was a desire for real meetings, but the current situation did
not permit to plan a concrete meeting.

The next virtual meeting will be June 6th 2022.