Re: XPath built-in datatype

(sorry for slow reply -- I've been busy with many parallel projects)

Just my opinion, not speaking for the WG or anyone else, but I think that 
an XPath datatype would be a fine thing for the XSL workgroup to declare. 
I think it is a mistake to ask schemas to go too far down the road in 
baking in every string-type that is motivated by some other W3C spec. 
Schemas gives other groups the power to create their own target 
namespaces, and to publish schemas with the appropriate type definitions. 
As noted below, validation of XPath strings can at best be somewhat loose, 
but you can easily provide a standard W3C-wide means to express that a 
string is intended as an XPath.   Admittedly, there is a slight 
circularity in the fact that schemas makes some use of XPath in 
structures.  I would still prefer to do the architecturally correct thing, 
and get the XSL WG lined up to publish an XPath type if the world needs 
one.  I would like to believe that we could sort out the corresponding 
trivial change to the schema for schemas during the CR period.  In 
general, groups that own particular namespaces should own the schemas for 
the corresponding datatypes, I think.  Yes, there is room for exceptions 
for convenience.

------------------------------------------------------------------------
Noah Mendelsohn                                    Voice: 1-617-693-4036
Lotus Development Corp.                            Fax: 1-617-693-8676
One Rogers Street
Cambridge, MA 02142
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"Arnold, Curt" <Curt.Arnold@hyprotech.com>
Sent by: www-xml-schema-comments-request@w3.org
04/06/00 01:47 PM

 
        To:     "'Chris Lilley'" <chris@w3.org>
        cc:     "'www-xml-schema-comments@w3.org'" <www-xml-schema-comments@w3.org>, (bcc: 
Noah Mendelsohn/CAM/Lotus)
        Subject:        XPath built-in datatype

From http://lists.w3.org/Archives/Public/www-svg/2000Apr/0014.html

Dan Connolly wrote:

> For more complex stuff (e.g. xpath notation), the schema spec doesn't
> provide any mechanism to express that syntax.

Chris Lilley wrote:
Pity.

It would seem a minimal burden to add a built-in datatype that allows you 
to declare an attribute (or element content) as conceptually being an 
XPath.  Since XPath is intended to be used across W3C
technologies, it would seem that the best place for it would be as a 
built-in type in Schema instead of every technology that uses it trying to 
kludge it with their own regular expressions.

<datatype base="string" name="XPath"/>

The difficulty is in the implied validation a schema aware processor is 
expected to do when it encounters an attribute that uses an XPath or 
derived datatype (in the same manner the parser is
anticipated to validate that a uri or Qname is valid beyond what is in the 
explicit Schema for Schema definitions).  If that seems like too much 
complexity, you could except conforming processors from
doing any implied validation of XPath's.  But compared to the overall 
complexity of Schema, an XPath type validation seems fairly trivial.

Received on Tuesday, 18 April 2000 11:53:01 UTC