- From: Mark Birbeck <mark.birbeck@webbackplane.com>
- Date: Mon, 16 Feb 2009 11:50:40 +0000
- To: Henri Sivonen <hsivonen@iki.fi>
- Cc: Sam Ruby <rubys@intertwingly.net>, Kingsley Idehen <kidehen@openlinksw.com>, Dan Brickley <danbri@danbri.org>, Michael Bolger <michael@michaelbolger.net>, public-rdfa@w3.org, RDFa mailing list <public-rdf-in-xhtml-tf@w3.org>, Tim Berners-Lee <timbl@w3.org>, Dan Connolly <connolly@w3.org>, Ian Hickson <ian@hixie.ch>
Hi Henri, > 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. I think at the level of the infoset that namespaces are useful, but at the level of user mark-up they are not. It's a bit like needing 'jump by an offset of 23 bytes if not zero' at the level of assembly language and machine code, with such a construct being irrelevant in a high-level programming language. 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. 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. 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. By saying that we are not using XML namespaces, but that @xmlns is one way to provide prefix mappings, we left the door wide open for other substitution mechanisms, and as Ivan said, work is underway to provide one or more alternative mechanisms to @xmlns. Mappings could be provided inline, using a new attribute, and in external files -- something that @xmlns is not capable of. At the moment the working title for the 'new attribute' mechanism is @prefix. Myself, I prefer @token for reasons that I'll be explaining in a forthcoming post, but the name is neither here nor there; it simply provides a way to create 'tokens' that can be used in strings that look like this: "dc:title". We strongly believe that once this mechanism is available, people will not bother using @xmlns. 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. Regards, Mark -- Mark Birbeck, webBackplane mark.birbeck@webBackplane.com http://webBackplane.com/mark-birbeck webBackplane is a trading name of Backplane Ltd. (company number 05972288, registered office: 2nd Floor, 69/85 Tabernacle Street, London, EC2A 4RR)
Received on Monday, 16 February 2009 11:51:23 UTC