- From: Ivan Herman <ivan@w3.org>
- Date: Tue, 18 Oct 2005 14:29:25 +0200
- To: Mark Birbeck <mark.birbeck@x-port.net>
- Cc: 'Sandro Hawke' <sandro@w3.org>, semantic-web@w3.org, 'public-rdf-in-xhtml task force' <public-rdf-in-xhtml-tf@w3.org>
- Message-ID: <4354EAA5.8040904@w3.org>
Hi Mark... thanks for the detailed explanation. Personally, I am a bit afraid of the Perl effect, when a term (or language construct) has zillion of implied and inferred semantics just to make things more consise. You had perfectly good arguments to keep the <whatever rel="rdf:type" href="something"> .... </whatever> separate and I would be in favour of keeping it that way. Ie, not having a hidden meaning added to 'role'. Whether somebody comes up with a handy abbreviation for this... well, that is another matter. It is worth a discussion around a table with a couple of beers... Just my two pence Ivan -------- Original Message -------- From: "Mark Birbeck" <mark.birbeck@x-port.net> To: "'Sandro Hawke'" <sandro@w3.org> CC: semantic-web@w3.org, "'public-rdf-in-xhtml task force'" <public-rdf-in-xhtml-tf@w3.org> Subject: Re:Question from the RDF-in-XHTML task force on the HTML Role Attribute Date: 18/10/2005 01:37 > Sandro, > > The XHTML role attribute was originally devised to help with accessibility > [1]. The idea was that you could put this attribute onto any element and > tell some processor what this element was doing. This would go for script > elements as much as for divs and spans. > > So in real-world usage, you might put role="hint" onto a div element, and a > server processor would know that when converting this particular HTML > document for a blind user--perhaps to VoiceXML--it should do something > clever with this 'hint'. > > That's all far enough, and as I'm sure you'll agree, there is nothing > controversial here in saying, for example: > > _:div0 xh:role wai:hint . > > (The WAI group is involved in defining a taxonomy that can be used as > objects in such statements.) > > However, the tricky bit comes next; if some elements are playing the 'role' > of a toolbar or menu on an XHTML page, is it legitimate to say that they > really 'are' toolbars or menus. In other words, simply by having a role > predicate, does our div also get an additional triple: > > _:div0 rdf:type wai:hint . > > The way that this extra triple is obtained is of course up for discussion > too--it could be that xh:role is owl:sameAs rdf:type, or there is a > hierarchy, or whatever--but that's not the question we need to resolve > first; initially we're keen to hear from the RDF community whether it would > be fair to say: > > if something plays the role of a toolbar, then it *is* a toolbar > > > Now, just in case people think we should just flip a coin and move on to > more interesting topics, I'll give you some of the arguments that make this > problematic. > > The main argument *against* this is that we may now get other statements > that are not helpful, by inference. Let's say that we have the following > XForms mark-up: > > <xf:input ref="surname"> > <xf:label>Surname:</xf:label> > <xf:hint>Please enter your name</xf:hint> > </xf:input> > > And let's say that we have agreed that the XForms specification provides us > with a ready-made taxonomy of controls (by that I mean that their behaviour > is defined abstractly and in a device-independent way). We can therefore add > roles to our XHTML 1.1 mark-up, as follows: > > <label for="sn" role="xf:label">Surname:</label> > <input id="sn" name="surname" role="xf:input" /> > <div role="xf:hint">Please enter your name</div> > > If a server was dealing with an ordinary HTML browser, it could pass this > code straight through, perhaps adding a reference to an external JavaScript > file on the way to help implement the hint. But with this definition a > server could also build the XForms mark-up we had, or an VoiceXML page. So > the role attribute has successfully helped to indicate to a server what each > element is doing. > > But although the div is playing the role of an XForms hint, it is not > actually a hint, and to infer that it was could be problematic. For a start, > in an HTML browser, the div needs event handlers defined to help the div > hide and show itself in response to mouse movements. The server therefore > needs to know that this div is an 'aspiring' hint, but it is not 'actually' > a hint. > > > The argument *for* having some form of equivalence between xh:role and > rdf:type is that it makes for a very handy shorthand. There are many > situations when writing RDF/A where you want to say that a div is playing > the role of a foaf:Person or a calendar entry, or whatever. At the moment > this is long-winded, and has to be done something like this: > > <div> > <link rel="rdf:type" href="[foaf:Person]" /> > Ben Adida > </div> > > (This uses the new CURIE syntax--it's still under discussion, but for now > think of it as a way of putting QName-like strings into places where URIs > normally go.) > > As you can see, this could get a bit much in situations where the primary > purpose of the mark-up is to carry a lot of metadata (as discovered by > Steven Pemberton who originally proposed this). > > Anyway, sorry that was so long, but I'm keen to ensure that people know why > we are discussing this, so that we can get a wide range of input on this. > > To summarise, the positions I can see on this issue so far, are: > > Either: > > * if something plays the role of something then it > *is* an instance of that thing; > > Or: > > * just because something has a purpose of X, doesn't mean it > that it is an example of X. > > I would add another line of discussion to this second position, which is > that we could still obtain the 'Pemberton-shorthand' in some other way, such > as adding another attribute, along the same lines as 'a' in N3. > > Of course there may be other views, but I hope we can get some comments on > these. > > Regards, > > Mark > > > [1] As far as I am aware the proposal originates from T. V. Raman--at least > the first draft I ever saw was authored by him (but apologies if anyone else > was also involved). I then worked with Raman on a subsequent draft that > brought in RDF and QNames, the idea being to make use of XForms and other > taxonomies, and also to help servers work out how to transpose, if > necessary. Eventually the whole thing was brought into XHTML 2. > > > Mark Birbeck > CEO > x-port.net Ltd. > > e: Mark.Birbeck@x-port.net > t: +44 (0) 20 7689 9232 > w: http://www.formsPlayer.com/ > b: http://internet-apps.blogspot.com/ > > Download our XForms processor from > http://www.formsPlayer.com/ > > >>-----Original Message----- >>From: public-rdf-in-xhtml-tf-request@w3.org >>[mailto:public-rdf-in-xhtml-tf-request@w3.org] On Behalf Of >>Sandro Hawke >>Sent: 17 October 2005 20:58 >>To: Ben Adida >>Cc: semantic-web@w3.org; public-rdf-in-xhtml task force >>Subject: Re: Question from the RDF-in-XHTML task force on the >>HTML Role Attribute >> >> >> >>Ben Adida writes [to www-rdf-interest]: >> >> >>>Here's a better example that's more related to one of our issues in >>>serializing FOAF documents: >>> >>>=========== >>><div role="foaf:Person"> >>>Ben Adida >>></div> >>>=========== >>> >>>which would yield a triple: >>> >>>=========== >>>_:div0 xhtml2:role foaf:Person . >>>=========== >> >>This is hard to understand without seeing the other triples >>would be generated. What is the proposed relationship >>between _:div0 and the literal "Ben Adida"? >> >> -- sandro >> >> >> >> > > > > > -- Ivan Herman W3C Communications Team, Head of Offices C/o W3C Benelux Office at CWI, Kruislaan 413 1098SJ Amsterdam, The Netherlands tel: +31-20-5924163; mobile: +31-641044153; URL: http://www.w3.org/People/Ivan/
Received on Tuesday, 18 October 2005 12:29:21 UTC