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Re: whitespace facet constrains value space of integer???

From: Dan Connolly <connolly@w3.org>
Date: Mon, 15 Sep 2003 11:51:52 -0500
To: "C. M. Sperberg-McQueen" <cmsmcq@acm.org>
Cc: www-xml-schema-comments@w3.org
Message-Id: <1063644712.5534.125.camel@dirk.dm93.org>

On Mon, 2003-09-15 at 10:30, C. M. Sperberg-McQueen wrote:
> On Mon, 2003-09-15 at 07:34, Dan Connolly wrote:
> > "integer has the following ˇconstraining facetsˇ:
> > 
> > ...
> > whiteSpace
> > ..."
> >   -- http://www.w3.org/TR/xmlschema-2/#integer
> > 
> > 
> > "[Definition:]  A constraining facet is an optional property that can be
> > applied to a datatype to constrain its ˇvalue spaceˇ."
> > -- http://www.w3.org/TR/xmlschema-2/#dt-constraining-facet
> 
> Oops.  That definition is at best misleading.

It misled me and a few others, yes.

>   Some
> constraining facets constrain the value space directly
> (e.g. maxInclusive) and some constrain it indirectly,
> as a consequence of the constraint they place directly 
> on the lexical space (e.g. pattern).  
> 
> The whitespace facet is slightly different from other facets 
> in that strictly speaking it describes what whitespace
> normalization is done during the process of getting from
> whatever data is presented at the higher level (in the
> usual case: the attribute value in the XML document or
> infoset) to the lexical form.  It constrains the value
> space and lexical space only indirectly (if at all).
> 
> I think we may want to class this as a problem requiring
> a clarification.
> 
> > So the whitespace facet constrains the *value space*
> > of integer somehow?
> 
> No.  The whitespace facet won't have any effect on the
> value space of integer.  It can have an effect on the
> value space of types derived from string (e.g. by guaranteeing
> that the lexical space contains no strings which contain
> any whitespace characters other than blank).  But when
> viewed as a constraint on the value space of integer, it's
> a vacuous constraint.
> 
> > Please clarify. The RDF Core WG is having a heck
> > of a time figuring out whether " 3 " is in the
> > lexical space of the integer datatype.
> > (This comment is not sent on their behalf, however.)
> 
> Ah, well that's simple.  The lexical space of integer
> is described thus:
> 
>    integer has a lexical representation consisting of 
>    a finite-length sequence of decimal digits (#x30-#x39) 
>    with an optional leading sign. 
> 
> No blanks are mentioned, and no blanks appear in any
> lexical form.

Yes, that's the way I understood it; but when I tried
to back my argument from the text of the spec, I found
that oddness above.

>   The whitespace facet for integer has the value
> 'collapse' (inherited from decimal), so that if I give 
> "  3 " as the value of an attribute declared as having type
> xsd:integer, it will be valid.  The XML document contains
> "  3 ", the infoset has "  3 " (unless the document has a
> DTD which causes normalization to "3"), the lexical form
> (after applying the whitespace=collapse rule) is "3", 
> and the value, of course, is succ(succ(succ(0))).
>   
> As we pointed out in one or the other of our comments to the
> RDF group, whitespace normalization is NOT part of type checking
> and should be provided for, if appropriate, by the higher-level
> system which uses the XSD types.

Yes, I saw that...

>   In our case, the Structures
> spec includes the rule that says "do whitespace processing
> before type validation"; if an RDF processor should do 
> whitespace normalization, the RDF specs need to say so.
> 
> The specific comment we made is at
> http://www.w3.org/XML/Group/2003/03/xml-schema-rdf-notes.html#ab2b3b3b9b3
> 
> If as you say the RDF Core WG to that comment if as you say
> they are having trouble understanding whether "  3 " is a legal
> lexical form for integer, I'd be grateful if you could point
> them at that comment.

Yes, they/we have seen it, and we've added a test to our test
suite to clarify that "  3  " isn't in the lexical space
and sent an "are you happy?" msg back, but
we found some misleading/conflicting info in the XML Schema
specs meanwhile, so it'll be nice to get WG-to-WG confirmation that
the misleading stuff is just a bug.

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Monday, 15 September 2003 12:51:53 UTC

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