[Bug 3224] Inequality

http://www.w3.org/Bugs/Public/show_bug.cgi?id=3224





------- Comment #4 from cmsmcq@w3.org  2006-09-22 13:14 -------
Thank you for the comment; it's so easy to overlook these things that outside
eyes are extremely useful.

The best thing I can think of, to resolve this, is to replace paragraph
2 of section 2.2.2, which currently reads:

    On the other hand, equality need not cover the entire value space
    of the datatype (though it usually does). In particular, NaN <>
    NaN in the precisionDecimal, float, and double datatypes.

with: 

    On the other hand, equality need not cover the entire value space
    of the datatype (though it usually does). In particular, NaN is
    not equal to NaN in the precisionDecimal, float, and double
    datatypes.

I have sketched out various alternative wordings that say explicitly
that NaN is not comparable to NaN, as well as being unequal, but 
have not been satisfied with them:  they have the same flaw you originally
pointed out (namely, they rely on a technical term defined later) and
I was not able to find wording that did not invite the question "and
why are you telling me this?"  

Of course, the reason for telling the reader that NaN is not comparable
to NaN is that one reader asked about it.  But re-reading your comments,
I wonder if talking about incomparability here would actually give the
correct insight:  incomparability, as the XSD 1.1 spec uses the term,
does not entail, or correspond to, an error in the comparison -- it's just
a relation on values, like other relations.  It is difficult, if not
impossible, to construct an example of comparisons across primitive
datatypes in a schema, and if one did succeed the spec does not prescribe
an error over the form of the comparison, only the result 'false'.

So with some regret I am proposing to leave the second part of your
comment unaddressed, although I believe on rereading the relevant parts of
the spec that the substantive question you raise is in fact answered by
the definition of comparability in section 2.2.3.

N.B. the Working Group has not yet taken action on this proposal.

Received on Friday, 22 September 2006 13:14:58 UTC