- From: Axel Polleres <axel.polleres@deri.org>
- Date: Fri, 27 Feb 2009 22:20:43 +0000
- To: Chris Welty <cawelty@gmail.com>
- CC: "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>
I do not formally object but have reservations against 3) because: i) pred:literal-equal/pred:literal-not-equal are then no longer "parametrizable" for any dialect, but always depend on the certain datatypes of BLD only, i.e. their definition would not extend to new datatypes and particular I am unsure about what that means for the definition of literal-not-equal (admittedly, didn't think about it in detail yet) Chris Welty wrote: > > Issue-80 was prompted by DaveR's attempt at using RIF-Core to specify > the rules in OWL-RL. He suggested it would be much easier, and also > promote datatype extensibility, if the builtins were more general. We > resolved to have a two-argument pred:isLiteralOfType (and its negation), > and are currently considering literal equality, which is more complicated. > > Basically we need a pred:literal-not-equal, or at the very least a not= > for each datatype. It seems to make sense to have a pred:literal-equal > as well (for symmetry, if nothing else), but what does it do? Is it > redundant with RIF's = predicate? Does it do numeric comparison? Is it > simply lexical? > > At the moment pred:literal-equal is defined to be subsumed by RIF's =. > It does not do xs:numeric-equal, which includes type promotion. Thus we > would need to keep that, unless this predicate were changed. RIF= for > datatype checks identity in the value space. > > Jos believed he read somewhere that it is possible for a datatype to > have multiple values in their value spaces that are identical. Probably > this is from dateTime, which is pretty hard to understand - I wasn't > able to nail it down precisely (the spec says datetimes are compared > based on their timeline values). Thus if RIF= already provides value > space identity, pred:literal-equal could provide the datatype specific > equality that F&O specifies for e.g. numerics, date-times, etc. > > Note: [XS2] says "Equality" in this Recommendation is defined to be > "identity" (i.e., values that are identical in the ˇvalue spaceˇ are > equal and vice versa). Identity must be used for the few operations that > are defined in this Recommendation. Applications using any of the > datatypes defined in this Recommendation may use different definitions > of equality for computational purposes; [IEEE 754-1985]-based > computation systems are examples. Nothing in this Recommendation should > be construed as requiring that such applications use identity as their > equality relationship when computing. > > Solutions: > > 1) Drop pred:literal-equal > 2) Leave pred:literal-equal as is (redundant with RIF =) > 3) Redefine pred:literal-equal to perform all the datatype specific > equality tests including numeric, and remove those datatype specific > tests from DTB. > > -Chris > > [Xs2] http://www.w3.org/TR/xmlschema-2/ > -- Dr. Axel Polleres Digital Enterprise Research Institute, National University of Ireland, Galway email: axel.polleres@deri.org url: http://www.polleres.net/
Received on Friday, 27 February 2009 22:21:27 UTC