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RE: What are the characteristics of a good type system for XML

• To: "Rick Jelliffe" <ricko@a...>,<xml-dev@l...>
• Subject: RE: What are the characteristics of a good type system for XML?
• From: "Dare Obasanjo" <dareo@m...>
• Date: Wed, 14 May 2003 09:45:43 -0700
• Thread-index: AcMZ2YfKFygf9lptS0OeMTCbcakzoQAWuncw
• Thread-topic: What are the characteristics of a good type system for XML?

I've seen two broad classes of users of W3C XML Schema. Those who want
to perform document validation to ensure that the contents of a document
satisfy some pretedetermined contract and those who want type augmented
infosets. The people in the former camp map to users of the
XmlValidatingReader in the .NET Framework and the latter folks are users
of the DataSet, .NET Framework XML Serialization and the SQLXML Managed
classes. 

Those that want validation can be satisfied with a "type system" where
the simple types are either strings or [named] regular expressions that
restrict the lexical space of a particular string. Those that want type
augmented infosets want them so that they can perform operations on
values depening on what types they are. They want to add numbers, sort
dates, concatenate strings, compare equivalence of values, substitute
and promote types,   etc. 

The failing of XML Schema is that they started doing the latter then it
seems like whenever they came across a problem they just pretended they
were doing the former. This gives us things like (xs:float & xs:double &
xs:decimal not being comparable), indeterminate sorting problems with
xs:duration, the (a + b) + c !=  a + (b + c) problem if a is an xs:date
and b and c are durations, lack of comparability of xs:hexBinary &
xs:base64Binary, types like xs:QName with no canonical form, and a host
of other issues. 

Amelia's proposal and the current discussion seems just as narrowly
focused, hence the train wreck analogy.  ;) 

-- 
PITHY WORDS OF WISDOM 
Any simple theory will be worded in the most complicated way.


This posting is provided "AS IS" with no warranties, and confers no
rights. 

>  
>  
> -----Original Message-----
> From: Rick Jelliffe [mailto:ricko@a...] 
> Sent: Tuesday, May 13, 2003 10:30 PM
> To: xml-dev@l...
> 
> From: "Dare Obasanjo" <dareo@m...>
> 
> > Defining a type system via the narrow lens of validation is 
> partly the 
> > cause of what many term the "brokenness" of W3C XML Schema and why 
> > some of our devs and testers (of which I used to be one) 
> have had some 
> > issues with the XQuery type system.
> 
> What fun: I have never heard anyone say XML Schemas pays too 
> much attention to validation (compared to issues related to 
> configuring DBMS and middleware!) Indeed, one of the points 
> with DSDL, RELAX, Schematron etc is that WXS does not meet 
> the mark for document validation, by providing to few bangs 
> for too many bucks.  
> 
> Dare, what is the brokeness of WXS as you see it, especially 
> that broken lens?
> 
> Cheers
> Rick
> 
> 
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• Follow-Ups:
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    • From: John Cowan <cowan@m...>
  • Re: What are the characteristics of a good type systemfor XML?
    • From: "J.Pietschmann" <j3322ptm@y...>

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