- From: Mark Birbeck <mark.birbeck@webbackplane.com>
- Date: Thu, 2 Dec 2010 12:14:06 +0000
- To: Ivan Herman <ivan@w3.org>
- Cc: Shane McCarron <shane@aptest.com>, Toby Inkster <tai@g5n.co.uk>, W3C RDFa WG <public-rdfa-wg@w3.org>
Hi Ivan, I guess in one sense left-right v. right-left doesn't make much difference. However, our processing rules generally have a sort of 'later overrides earlier' aspect to them, based on the hierarchical nature of the documents that we're parsing. Having a rule where the deeper nodes override their parents' values makes processing very easy. Now, of course you could say that 'latest wins' would still be the rule inside the @prefix attribute if we processed from right to left. But I do think that would be a little odd, given that conventionally people see the DOM hierarchy as going from left to right. To illustrate, our processing model would say that the second occurrence of 'foaf' in this example applies due to the hierarchy (in a sense, it's 'later overrides earlier'): <div prefix="foaf: http://blah1"> <div prefix="foaf: http://blah2"> <!-- use blah2 ---> </div> </div> Writing an example where the same prefix is defined in @prefix might look like this: <div prefix="foaf: http://blah1 foaf: http://blah2"> <!-- should really use blah2 ---> </div> </div> I think it would be counterintuitive if the left-most prefix was preferred over the right-most one, in this example. This simplicity of overriding is lost in the processing of profiles (as a result of the resolution you refer to on ISSUE-23). The way that the processing is now described in section 9 implies that you need to track each profile loaded to see if there is a conflict later. Of course, the easiest way to implement this is to process from right to left, which removes the need to track each profile, but then I think most implementers will rightly ask...why is everything else going from left to right, except @profile? We know that the only reason profile processing was made to work from right to left was due to the legacy use of @profile, in which only the first value had significance; some argued that this implied that the left-most profile should be the most important, and therefore should override others. Personally, I didn't find this very convincing (and the resolution didn't have great support), but we have the resolution now. However, given that we have the resolution to deal with a legacy issue, it should really be regarded as an anomaly, I it certainly shouldn't be used as a model for other processing rules. Regards, Mark On Thu, Dec 2, 2010 at 9:56 AM, Ivan Herman <ivan@w3.org> wrote: > Shane, > > there is no separate comment list; the reference in the document for comments is the WG mailing list... > > But yes, this _is_ a last call comment, though I thought it is an editorial issue. > > So, to make it clear, the question is what is the effect of @prefix="a: http://a.b a: http://c.d". In my original mail I said it should be left to right. But I since seemed to remember that we decided to have it right to left, ie, in my example, the result should be a->http://a.b. I tried to find a resolution in the mail archives, but I could not. However I did find this: > > http://lists.w3.org/Archives/Public/public-rdfa-wg/2010May/0123.html > > which led to a discussion thread on the relative priority within a @profile. This led to this resolution: > > http://www.w3.org/2010/02/rdfa/meetings/2010-06-03#resolution_7 > > ie, left-most declaration wins. I have not found any resolutions related to @prefix. However, based on the the resolution we have already taken for @profile I would propose to define the same order for @prefix and that should be documented in RDFa 1.1 Core > > Ivan > > > > > On Dec 2, 2010, at 02:01 , Shane McCarron wrote: > >> Since we are in last call, please submit this as a last call comment to the appropriate public list before the deadline. >> >> On 12/1/2010 6:16 PM, Toby Inkster wrote: >>> On Wed, 1 Dec 2010 11:21:55 +0100 >>> Ivan Herman<ivan@w3.org> wrote: >>> >>>> @prefix="a: http://a.b a: http://c.d" >>>> >>>> will end in a->http://c.d >>>> >>>> However, I tried to locate this in the document and I could not... >>> That's what I do, but I agree we need to make this explicit as it's a >>> case that implementors will definitely need to handle. >>> >> >> -- >> Shane P. McCarron Phone: +1 763 786-8160 x120 >> Managing Director Fax: +1 763 786-8180 >> ApTest Minnesota Inet: shane@aptest.com >> >> > > > ---- > 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, 2 December 2010 12:15:27 UTC