A call for reason

Gavin Thomas Nicol gtn at ebt.com
Mon Nov 29 06:09:12 GMT 1999


If you have a look at my posting of 11/15/99

  http://www.lists.ic.ac.uk/hypermail/xml-dev/xml-dev-Nov-1999/0500.html

you'll see that I basically agree with your logic. The point is that
you don't really need to define a new syntax, but rather define the
application conventions for using an existing syntax (ideally using
a sophisticated schema mechanism as you suggest).

Another way of looking at it would be to look at a stream of SAX
events as tokens of a language. You want to constrain the grammar
(the way the tokens can be organized), not the way the tokens
are formed.

> The XML 1.0 spec allows an application to accept and reject 
> any subset of XML; it only makes demands of the XML processor 
> that the application contains.  I believe this is in full 
> conformance with the spirit of XML as well, as it's only the 
> parsing technology that it strives to make universal.
> 
> Yet if the application is going to reject that comment or 
> that PI or that non-English element type name in the end, 
> what difference does it make to the outside world whether it 
> is the parser layer that makes the decision?  Each 
> application in a ring of applications exchanging XML is 
> already beholden to conform to a particular schema or set of 
> schemas, so it's already the business of this ring to decide 
> what constitutes acceptable XML.
> 
> Provided that the SML effort yields a subset of XML, as it 
> should, SML should end up being a label for a group of 
> document types -- nothing more.  One may then label an 
> application as SML-compliant.  Rings of SML-compliant 
> applications may surface, but for most uses such rings will 
> be further constrained to a finite set of document types.  If 
> we had a schema language of sufficient richness -- expressing 
> name production rules and general syntactic layout -- we 
> could even use it to express the SML class of document types.
> 
> What's wrong with defining classes of XML document types and 
> restricting applications to using XML belonging to these 
> classes?  The notion sounds useful for much more than 
> identifying the set of 'simple' document types.  Is this not 
> reasonable?


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