Sunday, February 02, 2003

Dare has a new post on shortcomings in the XSD type system.  Write the paper, Dare, I'd love to read it.  Dare made the point that XSD doesn't map well into OO type systems without adding AOP; for instance, when mapping simple type facets.  I'm not sure that this is necessarily a disadvantage, I think that it's just exposing the reality that OO type systems are a poor fit for a lot of real world data.  When mapping that data into OO, you have the choice of either loosely typing the data, using AOP techniques, or working up a clumsy mapping in OO.  I've seen and done all 3, long before XSD and before I ever started using XML.  The same goes for impedance mismatches between XSD and Relational data; people have struggled with OO-Relational mappings for even longer than XSD-Relational.  It doesn't help that some people insist that XML is the best and only form to store data, when they're just making work for themselves.  At the end of the day, property files, INI files, relational databases, and whatever else still have their place.  I'm interested in understanding the difficulties in performing those mappings, but I'm not ready to reject XSD out of hand.

To me, the most interesting part of Dare's proposed paper is his proposal for an XSD based language for processing XML.  Dare's comment is right on by me:

I'm definitely not sold on being able to map XML documents to classes but do see the value in being able to access the atomic values (i.e. simple types) in an XML document as strongly typed programming language primitives data instead of just text.

I'm not prepared to say that XSD is God's own type system.  But if He had a type system, I'll bet it looks more like XSD than Java.

11:17:58 AM  permalink Click here to send an email to the editor of this weblog. 


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