- From: Manu Sporny <msporny@digitalbazaar.com>
- Date: Sat, 02 May 2009 12:14:09 -0400
- To: RDFa Developers <public-rdf-in-xhtml-tf@w3.org>
Mark Birbeck wrote: >> It's because of this point that I think that "DEFAULTNS" would be >> preferable to a blank prefix identifier for changing the default namespace. >> >> I believe that we end up with a non-deterministic case if we allow >> arbitrary spaces between mappings and the equal sign AND try and use a >> blank prefix identifier to change the default namespace. Just to clarify - I was responding to Ivan's point and using the same terminology as to not confuse the issue further. I still believe that Ivan's point (how to set the default prefix) is a somewhat separate discussion from the point that you and Shane are making (the default namespace is not to be confused with the default prefix). I did make a mistake in calling it a namespace on the wiki page and in hindsight I probably should have straightened this out sooner on the mailing list (which, thankfully, Shane did). > The point that both Shane and I were trying to stress is that these > are *not* namespaces. > > Even when using @xmlns they are not namespaces. :) I agree that prefixes are not namespaces per the definition of 'namespace' in the XML sense, but I have a feeling that this community's decision to use xmlns is going to haunt us for a very long time. Specifically because we are ambiguous in the spec on the link between xmlns and prefix mappings. Here's our argument: RDFa uses prefix mappings to express bindings for CURIE prefixes. These are not namespaces as defined by the XML specification. and then we go on to state: XHTML1.1+RDFa uses xmlns to express these prefix mappings. The above statement is where we screwed up - we failed to see that people would assume that anything placed in xmlns would not actually have anything to do with XML namespaces. We abused the tag. Furthermore, the CURIE Syntax Specification even states[1]: """ When CURIES are used in an XML-based host language, and that host language supports XML Namespaces, prefix values MUST be able to be defined using the 'xmlns:' syntax specified in [XMLNAMES]. """ We're certainly setting up an environment where one might assume that there is a stronger link between xmlns and CURIE prefixes than what we intended. > They are prefix mappings, that just happen to be resident in the > @xmlns attribute. ...and people will just happen to assume a stronger link between xmlns and prefixes since xmlns is used to express this relationship. > But if we use @prefix (or @token, as I hope), then they lose even that > superficial relationship to namespaces. > > So we should drop that term completely from our discussions. There is much more than a "superficial" relationship to namespaces that "x:y" produces. We've re-hashed this discussion numerous times on the Microformats mailing list (but from the opposite direction), prompting an entire wiki page on the subject: http://microformats.org/wiki/namespaces-inconsistency-issue Personally, and I believe that I've made this clear during the telecons, is that we should run away from xmlns for defining prefix mappings as quickly as possible. We will not, however, be able to drop the term completely from our discussions. "x:y" does have a good bit to do with namespaces, in the traditional Computer Science sense of the word. Yes, it does not have anything to do with namespaces as is defined in [XMLNAMES], but it certainly does have something to do with the general concept of namespacing, which is described in [2]. Again, I agree with the concept that prefix declarations are not the same as namespace declarations and prefix mappings are not the same as XML namespaces. Prefix mappings do, however, have a relationship to the traditional Computer Science term "namespaces" - and I do think it is going to be very hard to teach the nuances to the web at large. So, I don't think we'll be able to drop the term completely from our discussions, and even if we could, I don't think that it would be the right way to go forward. -- manu [1] http://www.w3.org/TR/curie/#s_syntax [2] http://microformats.org/wiki/namespaces-inconsistency-issue [XMLNAMES] http://www.w3.org/TR/1999/REC-xml-names-19990114 -- Manu Sporny President/CEO - Digital Bazaar, Inc. blog: A Collaborative Distribution Model for Music http://blog.digitalbazaar.com/2009/04/04/collaborative-music-model/
Received on Saturday, 2 May 2009 16:14:53 UTC