- From: Ivan Herman <ivan@w3.org>
- Date: Thu, 30 Apr 2009 09:39:27 +0200
- To: Manu Sporny <msporny@digitalbazaar.com>
- CC: RDFa Developers <public-rdf-in-xhtml-tf@w3.org>
- Message-ID: <49F955AF.80107@w3.org>
Manu Sporny wrote: > Ivan Herman wrote: >> - Is the following acceptable: @prefix="=http://a.b.c/" ? >> my option would be yes, and it sets the default namespace. >> It could be equivalent to a xmlns="http://a.b.c/" > > Most of this discussion about changing the default namespace has > happened offline over the past couple of months. During the telecons, we > didn't discuss in detail or form a consensus on how one would override > the default namespace. > > The other option that has been floated over the past couple of months > was using a reserved word, so something like: > > @prefix="DEFAULTNS=http://a.b.c/" > I do not have very strong feeling about this but, I must admit, I am not sure I like the keyword approach, it adds yet another reserved term which is not good. I do not believe many people would use the default namespace stuff (after all, in 99% of the cases the default namespace is set by the surrounding language, eg, XHTML). > We could discuss further if a number of people felt that we needed a > mechanism to override the default namespace. It seems like we really > should define such a mechanism. > > Personally, I'd prefer a reserved word mechanism over the other method > because: > * It would probably be easier for non-developers to understand. 99.9% of the non-developers would not even consider this stuff in my view. They would just go with the namespace mechanism and rely on the surrounding language (XHTML) to have a default namespace. Ie, we should not go out of our way for this... > * It would be harder to mistakenly override the default namespace. Yes, that is a reasonable point... > * It would be easier for the parser writers to handle. > I am not sure of that... >> - Is the following acceptable: @prefix="aa=" >> my option would be no, this is an error, and the RDFa >> processor should simply ignore that > > I believe that the current regex would not match "aa=" and would thus > ignore it. However, if one were to do prefix="aa= bb=http://foo.com", > that may cause an issue. We should really have a couple of approved test > cases for these error conditions in the Design Suite. I'll try and take > an action to create some valid Design Suite test cases for @prefix. > Ie, we agree that this is an error, right? >> - What happens if there is, on an element, both an xmlns and a prefix? >> Ie, if I have >> >> <bla xmlns:aa="http://www.w1.com/" prefix="aa=http://www.w2.com/"/> >> >> what is the URI corresponding to the "aa" prefix? I know there were >> discussions on the task force, but it is not documented on the wiki... > > There are currently mixed feelings on this. At first, we believed that > xmlns and prefix would exist in the same language, but now there are > concerns that this may confuse people (having two ways to do the same > thing). This issue can be worked through, so let's assume that prefix > and xmlns can be defined in the same document. > > I believe that the current consensus is that you would process both > lists, but one would take precedence over the other. I agree. We should be prepared to have both (although future DTD-s could make one or the other not well formed, but that is another matter). Other than that we would force our tools to run in two 'modes' which complicates matters. > So, for example, if > @xmlns took precedence over @prefix, you would process @prefix first and > then @xmlns. Any conflicting mappings would be overwritten when @xmlns > is processed. The last defined value wins. > Exactly. So here is the $1000 question: what is the precedence? At the moment, in my tool (on my machine, that is) @prefix has a higher precedence, ie, that one wins, but it is really throwing a dice, as far as I am concerned. We just have to document the result of throwing it and declare victory on that one... (I do not really see a significant advantage of one over the other) Ivan > I have noted these issues on the rdfa.info wiki: > > http://rdfa.info/wiki/alternate-prefix-declaration-mechanism#Outstanding_Issues > > Anybody else disagree or have more input on these issues? > > -- manu > -- Ivan Herman, W3C Semantic Web Activity Lead Home: http://www.w3.org/People/Ivan/ mobile: +31-641044153 PGP Key: http://www.ivan-herman.net/pgpkey.html FOAF: http://www.ivan-herman.net/foaf.rdf
Received on Thursday, 30 April 2009 07:39:57 UTC