[Bug 3250] definition of precisionDecimal

http://www.w3.org/Bugs/Public/show_bug.cgi?id=3250





------- Comment #3 from noah_mendelsohn@us.ibm.com  2006-05-11 14:43 -------
Mike Kay writes:

> (There's a real procedural problem here in trying
> to define a data type in XML Schema and then
> lobbing it over the fence to QT to define some
> suitable operations. I personally have no idea how
> to define an arithmetic that is sensitive to the
> "precision" component of these values, yet that is
> presumably what QT are expected to do.)


Yes in principle, but in practice we're defining this type with the full
intention that it be (nearly) isomorphic to the one being defined in IEEE754r,
and as with binary floating point, the ieee draft does provide a useful suite
of operations (see http://754r.ucbtest.org/drafts/754r.pdf), and in fact a high
level but useful overview is available in the 754 wikipedia page: 
http://en.wikipedia.org/wiki/IEEE_754r#Operations.  Note that the draft
specification itself says:

" Each of the computational operations specified by this
standard, except those identified as reduction operations, shall be performed
as if it first produced an intermediate result correct to infinite precision
and with unbounded range, and then coerced this intermediate result to fit in
the destination's format (see Sections 4 and 7). Section 6 augments the
following specifications to cover ±0, ±, and NaN; Section 7 enumerates
exceptions caused by exceptional operands and exceptional results."

I think the implied relationship covers both the question of the general
motivation and intended tie to real world semantics for the type, as well as
the more formal specifics of what an appropriate suite of operations would be.

This seems to me to be a situation that's at least as good as for the Schema
1.0 types such as float.

Noah

Received on Thursday, 11 May 2006 14:43:46 UTC