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Re: RE: working with text (was RE: XPath 1.5?)

• To: Jonathan Robie <jonathan.robie@d...>
• Subject: Re: RE: working with text (was RE: XPath 1.5?)
• From: Uche Ogbuji <uche.ogbuji@f...>
• Date: Tue, 07 May 2002 11:20:35 -0600
• Cc: "Simon St.Laurent" <simonstl@s...>, Matthew Gertner <matthew.gertner@s...>, xml-dev@l...
• In-reply-to: Message from Jonathan Robie <jonathan.robie@d...> of "Tue, 07 May 2002 09:58:45 PDT." <5.1.0.14.0.20020507095459.04decec0@n...>
• Sender: uche.ogbuji@f...

> At 12:45 PM 5/7/2002 -0400, Simon St.Laurent wrote:
> 
> >It's very useful because the representation doesn't _require_ you to
> >process it in a particular way.  The looseness of the representation (as
> >Uche pointed out earlier) is actually a benefit for exchanging XML among
> >diverse processing environments.
> 
> Please illustrate this benefit with an example that is concrete enough to 
> evaluate. Show me an example where the typing of XPath 2.0 gets in your way.

Better.

The strong typing of XPath 2.0 makes it harder to understand and implement XPath 2.0.  Furthermore, the fact that XPath 2.0 has built in the concept of datatypes according to the XSDL canon forces out the development of generic typing for XPath.

Your earlier example:

avg( input()//person/salary )

I have no problem with your being able to take advantage of the knowledge that in your application context, this can be verified, optimized, and treated in various ways as befit some useful physical representation of the data.

Now, if I want to declare 

<irrnum>3.14</irrnum>

As an irrational number, and use the same capacity for verification, optimization, and treatment, can you tell me how to do so in standard XSDL and standard XPath 2.0?

The answer is that you cannot.  Why?  Because I cannot write a standard constraint of irrationality, since the XSDL group in their wisdom decided this is not an interesting data type.  I cannot even use their paltry extension mechanism for doing so.  I cannot use standard facilities for the optimization that you trumpet so loudly.

If we had a generic constraint mechanism, which might or might not be part of a schema definition language, and if this mechanism were modular enough not to overwhelm the basis of the XML specs that provided facilities for it, then I would have no complaint about addressing what I understand from this thread to be the sorts of use cases that drove XQuery, XPath 2.0 and XSLT 2.0.


-- 
Uche Ogbuji                                    Fourthought, Inc.
http://uche.ogbuji.net    http://4Suite.org    http://fourthought.com
Track chair, XML/Web Services One (San Jose, Boston): http://www.xmlconference.com/
DAML Reference - http://www.xml.com/pub/a/2002/05/01/damlref.html
RDF Query using Versa - http://www-106.ibm.com/developerworks/xml/library/x-think10/index.html
XML, The Model Driven Architecture, and RDF @ XML Europe - http://www.xmleurope.com/2002/kttrack.asp#themodel

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