xml-dev - Re: [Fwd: ATTN: Please comment on XHTML (before it's too late)]

[David Megginson <david@megginson.com>]

W. Eliot Kimber writes:

 > As I said in my post, the reverse is possible: a semantic definition
 > (e.g., XLink, RDF, XHTML) can state a binding as part of its
 > specification (which is exactly what the XLink spec does), but you have
 > know about that statement before you start processing a document. To do
 > that, you have to read the spec. Once you read the spec, the use or
 > non-use of name spaces is irrelevant for the purpose of recognizing
 > element types defined in a given spec--there are any number of ways
 > names can be disambiguated or bound to name spaces. The namespace
 > mechanism is only one, and it's a particularly weak one at that.

The first part of the statement is a truism -- with few (if any)
exceptions, there are always different ways any standard could be
implemented.  IP could have been designed dozens of different ways,
but that does not make IP irrelevant.

In fact, SGML itself (and XML 1.0) define only names scoped to a
specific document type, so there are two types of a-priori knowledge
necessary to recognize names:

1. You have to know (somehow) what the document type is (as Eliot has
   often pointed out, the DOCTYPE declaration doesn't help); and

2. You have to know (somehow) what the element or attribute name
   means.

There have been two significant attempts to remove the first of these
problems, so that arbitrary names can be recognized in any document:
Architectural Forms and Namespaces.  To establish names that can be
recognized outside of document types, it is necessary to make them
globally unique: Architectural Forms does so by associating each name
with a formal public identifier, while Namespaces does so by
associating each name with a URI.

Neither Architectural Forms nor Namespaces can offer a solution to #2
-- after all, the range of possible meanings is potentially infinite.
You can choose an arbitrary subset of possible meanings, either
generic (like HyTime) or specific (like HTML), but a human still has
to have read the spec and design software to do something useful.


All the best,


David

-- 
David Megginson                 david@megginson.com
           http://www.megginson.com/

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