[Bug 2970] Datatypes 2006-02-17 WD: merge precisionDecimal and decimal

http://www.w3.org/Bugs/Public/show_bug.cgi?id=2970





------- Comment #3 from davep@iit.edu  2006-09-15 16:29 -------
(In reply to comment #2)
> I remember some of the discussion for aligning these types in the hierarchy
> before when I was involved with the WG, but I don't remember the option
> presented in my original comment here ("minimal precision") being considered. I
> mainly remember a proposal where precision=absent for xs:decimal, but that
> expands the value space of xs:precisionDecimal since the latter doesn't allow
> precision=absent for numeric values.

Actually, both were worked out and considered.  For the variant you remember,
you have mentioned one difficulty.  For both, there has to be new,
special=purpose facets to accomplish the derivation, which would have to be
tracked; if those facets exist, then other users could use them to create
other-namespace, other-named versions of decimal that could not be recognized
by name and would make recognization for optimization difficult.  In addition,
either proposal changes decimal from primitive to derived, which IIRC makes
unfortunate trouble for F&O.

> What is the extra machinery for treating xs:d as a "minimal precision" xs:pd
> (and xs:integer as an integral-presicion xs:pd)? I take it instead of different
> lexical mappings, you would have a shared lexical mapping that is conditioned by
> a precision-mapping facet, whose values would be exact, minimal, or integral.
> Any other machinery or is that already too much?

"Too much" is, of course, in the eye of the beholder.  But requiring a lexical
mapping that must depend for its results on a facet value introduces several
complications:  One is that no libraried mappings work this way, so
implimentations must always add their own wrapper.  Another is that technically
a datatype exists on its own, independent of any simple type definitions that
"point at it" and link it to a name.  For that datatype to have to have
knowedge of those simple type definitions is a whole new version of datatype
which (at least it's my impression that) the WG is not prepared to work out on
the schedule it must work to to get to publication.

Received on Friday, 15 September 2006 16:30:03 UTC