Another look at namespaces

[Paul Prescod]

There are two separate issues here. 

#1. In 1999 XHTML can either have three namespaces or one. If it has
three then there will be a one-to-one relationship between namespaces
and grammars so that a programmer can know the grammar of the input
data. Programmers that want to treat the three as one will have to do so
by issuing some command to their namespace processor or (better) by
usuing a namespace processor that recognizes an embedded instruction.

Either way works because programmers know today what to expect and can
write their code accordingly. Hell, we could have one namespace per
element type or one namespace for all W3C specifications and you could
still write code that works.

I think that people are really concerned more about the precedent than
today's issue.

#2. In 2000, 2001, 2002, etc. there will be new versions of XHTML. Some
(probably all) of these will be backwards incompatible as every version
of HTML has been backwards incompatible: a document conforming to the
new vocabular/grammar can break code expecting the old
vocabulary/grammar. 

It is *vital* that a) there be a way to announce this
backwards-incompatibility and b) there be an infrastructure that allows
a mapping from new to old. The namespace is the obvious way to do the
former. We have no good mechanism for the latter.

As I've said, this is also necessary for e-commerce and every other XML
application.

If we develop this mechanism now then the first wave of XHTML software
will be automatically ready for XHTML 2.0 (not to mention e-commerce). I
can understand the wish to delay the problem but it just means that we
cause a train wreck later on. I am deathly afraid, however, that if we
set a precedent of pretending that these three variants are "one
language" we will continue down that path as we develop more and more
incompatible new versions.

 Paul Prescod

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