Re: [xml-dev] Victory has been declared in the schema wars ...

[Paul Downey <paul.downey@whatfettle.com>]

On 29 Nov 2006, at 11:32, Costello, Roger L. wrote:

> Would you explain why grammar-based languages (e.g., DTD, XSD, RNG)  
> are
> a bad foundation?  A grammar-based language tells an instance document
> author what tags are allowed, how those tags may be arranged, and the
> datatypes of the data.  Isn't that what we want from a schema  
> language?
> Shouldn't that information serve as the foundation for a schema?
>
> Also, would you explain why paths (XPaths) provide a more suitable
> foundation?

I'm not Rick, but here's my thinking:

When used as a description to drive a mapping (databinding if you will)
grammar-based languages encourage a parser to traverse the tree
or state-event the angle brackets and push the conten into the model
as it's encountered and barf if anything unexpected gets in the way.

This leads to closed world models, the need to add stupid flags such
as "mixed" and "xs:any", as well as enabling premature optimisations
such as UPA.

The result is a the natural tendency to kill extensions and evolution,
wither the 'X' in XML.

OTOH paths are ways of flagging the interesting bits in some otherwise
possibly open-ended content, and encourge querying the data. It's looser
and all the more loverly for it.

Paul
--
http://blog.whatfettle.com