ISSUE-70: Should CORE be decideable

CoreSafe

Should CORE be decideable

State:

CLOSED

Product:

Core

Raised by:

Dave Reynolds

Opened on:

2008-08-20

Description:

Should CORE have some form of safety constraint?

** Why might we want a safety criterion?

If it eases implementation so increasing the number of systems that can be fully conformant with CORE and so inter-operate via it.

For example, some existing systems perform a safety check and so could not implement a CORE that permitted more general rules.
A concrete example of this is DLV, as discussed in:
http://lists.w3.org/Archives/Public/public-rif-wg/2008Aug/0052.html

Which classes of potentially unsafe rules can in fact be executed depends upon execution strategy so that permitting such rules may exclude some execution strategies and again limit interchange. See examples are given by Axel in the above email.

** Why might we not want this?

If the safety check itself is hard for developers to understand and implement it may limit up-take.

If the safety criteria are conservative they may exclude rule sets which are of practical interest for interchange. For example:
s(?x) :- s(?y), add(?y, 1, ?x), ?x < 10.
s(0).
has a finite set of ground entailments implementable by both PRD and BLD systems but fails at least some of the proposed strict safety criteria.

** Solution approaches mentioned so far:

(a) Yes. Define a strict safety criteria such as domain-safety as suggested by Jos in:
http://lists.w3.org/Archives/Public/public-rif-wg/2008Aug/0026.html

(b) Yes. Restrict use of builtins to non-recursive safe bindings as proposed by Axel in:
http://lists.w3.org/Archives/Public/public-rif-wg/2008Aug/0028.html
http://lists.w3.org/Archives/Public/public-rif-wg/2008Aug/0052.html

(c) No safety constraint. But limit the conformance requirement. For example define conformance only over ground entailments of rulesets for which that is finite.

(d) No safety constraint, no conformance limitation.

Related Actions Items:

No related actions

Related emails:

1. Re: [Admin] Agenda for RIF telecon 4 November (from axel.polleres@deri.org on 2008-11-03)
2. [Admin] Agenda for RIF telecon 4 November (from csma@ilog.fr on 2008-11-03)
3. Minutes of RIF Telecon 14 Oct 2008 (from staylor@abdn.ac.uk on 2008-10-14)
4. [Core] Core telecon Monday, October 13 -- Notes (from Harold.Boley@nrc-cnrc.gc.ca on 2008-10-13)
5. [Core] Core telecon Monday, October 13 (from Harold.Boley@nrc-cnrc.gc.ca on 2008-10-10)
6. Re: [Core] PROPOSED Core resolutions from telecon Monday, September 22 (from debruijn@inf.unibz.it on 2008-09-26)
7. RE: [Core] PROPOSED Core resolutions from telecon Monday, September 22 (from palbert@ilog.fr on 2008-09-24)
8. RE: [Core] PROPOSED Core resolutions from telecon Monday, September 22 (from pvincent@tibco.com on 2008-09-23)
9. [Core] PROPOSED Core resolutions from telecon Monday, September 22 (from Harold.Boley@nrc-cnrc.gc.ca on 2008-09-23)
10. ISSUE-72 (Skolem functions in Core): Should Core support some approximation to skolem functions? [Core] (from sysbot+tracker@w3.org on 2008-08-21)
11. ISSUE-70 (CoreSafe): Should CORE be decideable [Core] (from sysbot+tracker@w3.org on 2008-08-20)

Related notes:

Display change log