On Feb 16, 2009, at 13:50, Mark Birbeck wrote:
Why was RDFa specified to use xmlns:foo when it was obvious that
people
would want to deploy it as text/html and you should have known that
HTML
parsers handled xmlns:foo differently from XML parsers?
Ah...now that is a fair question. :)
I am no great fan of XML namespaces either. In my view they were
created for a world of interlocking/interchangable documents that
simply never happened.
Here we have agreement.
However, given that many W3C standards rely on XML namespaces, we felt
that we would face problems if we tried to progress RDFa using a
prefix/mapping mechanism that did *not* use XML namespaces.
It seems bad if syntax with technical issues is chosen for political
reasons.
This reminds me of the ARIA naming debate. Towards the end of the
debate, it felt like proponents of the colon were more interested in
keeping up the syntactic appearance of Namespaces than actually
protecting a Namespace-wise architecturally sound programming model.
So we took a pragmatic decision; we realised that at some point we
would use a simple attribute to specify token mappings, but for the
first pass through of RDFa, we thought we should provide a less
'controversial' mapping mechanism.
Evidently, the mechanism you chose isn't exactly uncontroversial.
Note that one option would have been not having a mapping mechanism at
all: Using full URIs. (After all, if full URIs as identifiers aren't a
problem, why have a mapping mechanism?)
We did however, make some important steps away from XML namespaces,
though. Of course, we didn't get a smooth ride, but we started by
making the move away from QNames. We devised CURIEs, which are strings
with a simple substitution mechanism, and we said that XML namespaces
are simply *one* possible source of tokens for doing that
substitution.
I think having many sources of prefixes introduced over time is not an
improvement.
By saying that we are not using XML namespaces, but that @xmlns is one
way to provide prefix mappings
A problem with using @xmlns as opposed to using Namespaces it is that
strictly correct XML+Namespaces APIs down to expose @xmlns as an
attribute at all.
We strongly believe that once this mechanism is available, people will
not bother using @xmlns.
Who is "we" in this case?
Although it took time, and had to be done in a couple of steps, we
will have then completed the transition away from XML namespaces.
That sounds promising. :-)
--
Henri Sivonen
hsivo...@iki.fi
http://hsivonen.iki.fi/
