W3C home > Mailing lists > Public > public-rdf-in-xhtml-tf@w3.org > June 2007

Re: Blank nodes & classes

From: CÚdric Mesnage <cedric.mesnage@lu.unisi.ch>
Date: Fri, 22 Jun 2007 18:44:50 +0200
Message-Id: <281763B8-D873-44E6-A5F7-7D91C0B0D625@lu.unisi.ch>
Cc: public-rdf-in-xhtml-tf@w3.org
To: mark.birbeck@x-port.net



> I'm open to leaving this entire issue until a future version, if
> people have trouble with it. But since I do actually have an action
> item pending to work through the whole rdfs:label issue more generally
> (i.e., not just with <img> but in other places too), hopefully you'll
> forgive me if I use your post as a sounding board for some thoughts.
> ;)

I do forgive you :-)


> With respect, that's the point of RDFa. It's mostly about
> interpretation. If an author who is unfamiliar with RDFa writes this:
>
>  <a rel="p" href="o>Some link</a>

So in this case you want to infer:

<o> rdfs:label "Some link".

and this would have the same semantic value as the triple that I  
could define further in the document:

<span about="o" property="rdfs:label"> L'histoire d'O </span>

corresponding to <o> rdfs:label "L'histoire d'O".

So these 2 triples are interpreted and describe the same thing, one  
is explicit, one is not but I have no way to figure out (from an  
application point of view) which one was explicit, which one was not.

<o> rdfs:label "Some link".
<o> rdfs:label "L'histoire d'O".

The semantics of rdfs:label is "A human-readable name for the  
subject." and it is not "A piece of string which might describe the  
subject in a human readable form within the context it was found". So  
I still disagree of using automatically interpreted rdfs:label.

I agree with you on the idea that currently this information is lost  
and that we might want to interpret it. What about creating an RDFa  
vocabulary?

<o> rdfa:link_caption "Some link".

and in the case of img :

<o> rdfa:img_caption "Some image".

and in the more generic case of your prime minister example

<http://people.org/tony-blair> rdfa:caption "Prime Minister"

or rdfa:caption all the time with this property defined as "Text used  
in context to describe or identify the subject" ??


Best Regards, CÚdric
> then we've agreed that from RDFa's perspective, it is safe to
> interpret this as a triple, as follows:
>
>  <> p o .
>
> Why is it safe? Because the HTML spec itself comes about as close as
> you could get to saying so. It says that @rel represents a
> relationship between the current document and some target document. Of
> course it doesn't mention RDF, but it just happens to be that RDF is
> the most well known and well developed method of serialising
> statements such as "this document stands in an 'x' relationship to
> that document".
>
> Now, given that what we're doing is largely about interpretation of
> the HTML specification--putting aside new attributes like @about and
> @datatype--it's perfectly legitimate to ask what else is the author
> doing when they do this:
>
>  <a rel="p" href="o>Some link</a>
>
> Since every browser will display (or speak) this text in a way that is
> different to the surrounding text, and further, given that this text
> is invariably a link via which a user can navigate to a new resource,
> I think it's pretty safe to say that this is a "human readable label
> for the resource 'o'", which is, as luck would have it, the definition
> of rdfs:label. :)
>
> Continuing the point, but returning now to the example using @about,
> let's say I have the following text in my document:
>
>  The Prime Minister today flew to Russia.
>
> As it stands we don't know which Prime Minister, or on which day. If
> our author now does this:
>
>  The
>  <span about="http://people.org/tony-blair">Prime Minister</span>
>  <span content="2007-06-22" datatype="xsd:date">today</span>
>  flew to
>  <span about="http://countries.org/russia">Russia</span>.
>
> they have made quite an explicit connection between fragments of text
> and a resource. It seems to be really stretching things to say that we
> might cause problems if we interpret those fragments of text as 'human
> readable labels', since it's clear that they are.
>
> To illustrate, imagine for a moment that Google started indexing the
> RDFa in these kinds of documents. If I search in Google for "Prime
> Minister", would it not be legitimate to ask me if I'm looking for
> articles specifically about a particular Prime Minister, and if so,
> show me a list of them from different countries, and from the past? It
> would seem from the mark-up above legitimate to have in that list of
> Prime Ministers the person identified by the resource
> "http://people.org/tony-blair". But you could only draw that
> conclusion if we agree with this proposition:
>
>  <http://people.org/tony-blair> rdfs:label "Prime Minister" .
>
> Note that this statement does not rule out other labels which our
> 'Semantic Google' might have picked up as it scoured documents across
> the web:
>
>  <http://people.org/tony-blair> rdfs:label "Tony Blair" .
>  <http://people.org/tony-blair> rdfs:label "the Leader of the  
> Labour Party" .
>
> etc.
>
> But note that none of these are 'harmful' statements, since they are
> true; someone, somewhere, used one of these labels as a way of
> identifying the resource "http://people.org/tony-blair".
>
>
> So, the key point is that if the author attaches some metadata to a
> particular piece of mark-up then they have not only made statements
> via the metadata that they have added, but they have also made a
> statement by choosing one place to put their mark-up over another.
>
>
> However, as I said to Ivan, there is no big deal in leaving this open
> for discussion in a future version of RDFa. All I want to stress here
> is that such interpretations *do* make sense, since many (not all, of
> course) are given by HTML itself.
>
>
>> ... even worse an automatic interpretation which
>> by definition will be wrong in many cases or if not wrong, will be
>> different than what the developer/publisher meant. Moreover, the
>> piece of information which semantics were not explicitly defined by
>> the publisher does not seem to be of interest, it might be more
>> important to automatically infer the triple :
>>
>> <> rdf:li <http://whatever.org>
>>
>> or  <> dcel:relation <http://whatever.org>
>>
>> as the only thing that was said by the publisher is that this
>> resource is related to whatever :-)
>
> I guess you could say that, but you might then be in danger of putting
> the RDFa cart before the HTML horse. If I place the following in a
> document:
>
>  <img src="my-picture.jpg" alt="Me on holiday" />
>
> then I *really* have added an image. We might not (yet) know what
> triples to generate to indicate that we have an image--should we say
> xh:img, or dcmitype:Image, or foaf:Image, or whatever--and because of
> that I'm happy to leave the detail of the question to a future
> version. But the point is that the author's intent is pretty clear,
> and we might as well preserve that information in some form or
> another.
>
>
> One final thing; it's worth pointing out that most of the discussion
> on this list seems to come from people consuming or generating RDFa on
> servers. However, when you start to try to do things with RDFa in the
> client you find that you often need some of the context information,
> and rdfs:label is a fairly simple--non-invasive--means of retaining
> some context, that does not go against what can be derived from how
> the author has chosen to mark up a document.
>
> Regards,
>
> Mark
>
> -- 
>  Mark Birbeck, formsPlayer
>
>  mark.birbeck@x-port.net | +44 (0) 20 7689 9232
>  http://www.formsPlayer.com | http://internet-apps.blogspot.com
>
>  standards. innovation.
Received on Friday, 22 June 2007 16:43:12 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 21:50:23 UTC