Hell Mark Thanks for your reply... Mark Birbeck wrote: > Hi Martin, > > I do agree with the idea that there shouldn't be two ways to do the > same thing, but I feel the way to resolve that is to say that @prefix > is doing something different to @xmlns. > > And then drop the @xmlns technique. :) > > Right I didnt know that was the intention.... > The 'something else' that we should allow is the defining of full > URIs, and not just prefixes, and I've discussed this and some related > ideas in a recent blog post: > > <http://bit.ly/JKSgb> > Intresting post Mark thank you... > > On @xmlns itself, I think there are two major problems with it. > > The first is that it is essentially a technique for defining document > 'structure', rather than document 'content', so it seems wrong to me > to mix the two. (Lots of languages mix the two, it's true, and they > have tended to have problems.) > > Setting parts of a document's structure using namespaces is fine: > > <a:b xmlns:a="blah"> > ... > </a:b> > Agreed, I had never considered it. It looks like RDFa needs something like xmlns: but for "content" not "structure" .... > The content of a document could be regarded as being 'carried' by this > structure, and so can be seen as being in a different 'plane' or > 'axis'. (And by content I mean the text and the metadata.) > > However, there is no relationship between the document structure and > the document content. The source of elements and attributes from > vocabularies like XHTML and SVG is almost always different to the > source of properties from vocabularies like FOAF and DC. > > So just as there is no connection between namespaces used in a > document's structure and the title of the document, so there is no > connection between the namespaces and the metadata. > > If that seems a little esoteric, a simpler way to look at it might be > this; if you declare the SVG namespace in a document are you likely to > use that namespace mapping in any of your metadata? Or conversely, if > you declare the FOAF namespace in your document for use in @rel and > @property, are you likely to use that namespace mapping in your > element and attribute declarations? > > Almost certainly no, in both cases. > Right... > So I feel that the first thing we need to do is drop all references to > the term 'namespace' if we are going to provide a new attribute for > declaring prefixes. And if we do that then there is no need for a > discussion about overriding default namespaces, and such like. > > (And I should add that using @content would really confuse things.) > LOL yes it would thinking about it now.... > I said there were two problems with @xmlns; the second is that > namespaces apply to the element they are on, and the children of that > element. This makes it impossible to define a set of prefixes in an > external document, and then to import them. > > However, by devising a new attribute that owes no loyalty to the way > that @xmlns behaves, we can create new rules about processing, and in > particular allow for importing external collections of mappings. > > maybe try using the @prefix element in the same way @xmlns is used then?..... eg: <div prefix:foaf="http://xmlns.com/foaf/0.1/" rel="foaf:page" typeof="foaf:Document"> </div> setting the default prefix for an element could be achieved like this... <div prefix="http://xmlns.com/foaf/0.1/" rel="page" typeof="Document"> </div> which would be very RDFa like, and bonus... no talk about namespaces ;) Best Wishes Martin > Regards, > > Mark > > On Thu, Apr 30, 2009 at 12:07 PM, Martin McEvoy > <martin@weborganics.co.uk> wrote: > >> Manu Sporny wrote: >> >>> 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 >>> >>> >> Hello Manu Ivan , thank you Manu for documenting this. >> >> Im still a little unsure of why RDFa should support an alternate prefixing >> mechanism, its never a good thing in my view to support two ways of doing >> the same thing? >> >> I really do not like the @prefix mechanism at all it seems intuitive and a >> little "hackish". If RDFa really neds to support such a mechanism I am more >> in favour of re-using what we already have and not thinking of something >> new, @content seem ideal for this purpose >> >> <div content="foaf=http://xmlns.com/foaf/0.1/" >> rel="foaf:page" >> typeof="foaf:Document"> >> .... >> .... >> </div> >> >> multiple prefixes can also declared in this way eg: >> @content="foaf=http://xmlns.com/foaf/0.1/ dct=http://purl.org/dc/terms/". I >> prefer @content over @prefix because authors already know what it means. >> >> I dont believe any of these should be legal >> >> * foo= >> # would this default to the current document? >> >> * =http://someuri.com/ >> # why would you want to overide the default namespace? >> >> * xmlns:foo="http://foo.com" @prefix="foo=http://bar.com/" >> # on the same element seems pointless as you cant really differentiate >> the URI's, you cant do that in RDF so why should you be able to do that in >> RDFa? >> >> * I also think this should be Illegal @prefix="audio= >> http://purl.org/media/audio# video = http://purl.org/media/video#" >> # spaces between the "=" equals. >> >> >> Thank you. >> >> -- >> Martin McEvoy >> >> http://weborganics.co.uk/ >> >> "You may find it hard to swallow the notion that anything as large and >> apparently inanimate as the Earth is alive." >> Dr. James Lovelock, The Ages of Gaia >> >> >> >> > > > > -- Martin McEvoy http://weborganics.co.uk/ "You may find it hard to swallow the notion that anything as large and apparently inanimate as the Earth is alive." Dr. James Lovelock, The Ages of GaiaReceived on Friday, 1 May 2009 11:12:11 GMT
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