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 17:04:28 +0200
Message-Id: <ECE59785-DB51-4FBD-A900-7352AEDDA32B@lu.unisi.ch>
Cc: public-rdf-in-xhtml-tf@w3.org
To: mark.birbeck@x-port.net


On Jun 22, 2007, at 2:22 PM, Mark Birbeck wrote:

>> I am strongly against using URIs to identify resources...
>
> I think that's a discussion for another list. :)

all right, let's not discuss it further then.

> In other words, if you believe that we shouldn't take anything from
> the structure of the document, then we really should spell everything
> out.

It's not what I meant, we should make use of the structure of the  
document, but we shouldn't infer too much, when you say that :

<span about="http://whatever.org"> food book</span>

corresponds to the triple

<http://whatever.org> rdfs:label "food book".

it is an interpretation, 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 :-)

> As it happens, in my view rdfs:label is *exactly* right for this. The
> definition of rdfs:label says nothing more than that rdfs:label is a
> human readable label for a resource. I really don't think a big leap
> in logic is being if we were to assume that an author who tags some
> text with @about is making exactly that statement.
>
>
>> The question seems not to be what is the minimum markup that  
>> should give a
>> triple but more :
>>
>>  what is the minimum markup to generate the maximum triples...
>
> They are two separate issues. The 'what is the minimum?' question
> concerns trying to make things easy for authors to add useful
> information. So if I have a blog and I mention a couple of books and a
> company, should I need to specify more than an @about on a <span>? I
> think it would be great for ease of use and adoption of RDFa if it was
> not necessary. However, adding a @class value is not so much extra
> work, and that's good enough for now.
>
> But in terms of 'minimum mark-up, maximum triples' then all of your
> examples that follow are perfectly fine. How far you go with packing
> lots of attributes onto an element depends only on whether the mark-up
> will ever be read by a human or not. :) Particularly your last
> example, since a human reader might not immediately spot that some of
> the attributes are attached to the bnode. But like I say, it's
> certainly all correct. :)
>
>
>> Can we have :
>>
>> <span about="http://amazon.com/ISBN:0091808189"
>> property="rdfs:label" class="bib:book">
>>  Canteen Cuisine
>> </span>
>>
>> which would give:
>>
>> <http://amazon.com/ISBN:0091808189> rdf:type bib:book.
>> <http://amazon.com/ISBN:0091808189> rdfs:label "Canteen
>> Cuisine".
>>
>> and to go back to my example with Ben's solution:
>>
>> <div class="foaf:Person" rel="rdf:li">
>>  some things about the person
>> </div>
>>
>> which gives the triples :
>>
>> <> rdf:li _:whatever.
>> _:whatever rdf:type foaf:Person.
>>
>> Can we go further than that and do :
>>
>> <div class="foaf:Person" rel="rdf:li" property="foaf:name">
>>  CÚdric Mesnage
>> </div>
>>
>> or even :
>>
>> <div class="foaf:Person" rel="rdf:li" property="foaf:name"  
>> content="CÚdric
>> Mesnage"/>
>>
>> and get:
>>
>> <> rdf:li _:whatever.
>> _:whatever rdf:type foaf:Person.
>> _:whatever foaf:name "CÚdric Mesnage".
>>
>>
>>
>> ---
>> CÚdric Mesnage
>> PhD Student
>> cedric.mesnage@lu.unisi.ch
>> http://www.cedricmesnage.org
>> http://blog.cedricmesnage.org/
>>
>>
>>
>> On Jun 21, 2007, at 12:10 PM, Mark Birbeck wrote:
>>
>> Hi Ben/CÚdric,
>>
>> [I'm not proposing a resolution to this question in this version of
>> RDFa, but I think it's useful to collect use-cases.]
>>
>> I had a use-case the other day that is related to the ones you are
>> describing. Essentially the question we all seem to be converging on
>> is what is the minimum amount of mark-up that should give us a  
>> triple?
>>
>> So, the following feels quite natural, as a way of marking up the
>> mention of something like a book in my blog:
>>
>>  Today I bought a copy of
>>  <span about="urn:ISBN:0091808189" class="bib:book">
>>    Canteen Cuisine
>>  </span>
>>  from my local bookshop.
>>
>> Since my system uses the URI to retrieve some data about the book  
>> from
>> a book site like Amazon, I don't actually need any further triples
>> like title, price, publisher, author, or whatever. But there is a an
>> interesting question as to whether the following should be enough to
>> get an entry in the triple store:
>>
>>  <span about="urn:ISBN:0091808189">
>>    Canteen Cuisine
>>  </span>
>>
>> The system could still do the same thing, and retrieve additional
>> triples based on the resource, but the question is what are the
>> parsing rules that get from this mark-up to a triple?
>>
>> The only way I can think of to achieve this from the mark-up I've
>> shown is be automatically generate labels from the content of
>> elements. The mark-up would therefore generate this:
>>
>>  <urn:ISBN:0091808189> rdfs:label "Canteen Cuisine" .
>>
>> and we would now have the URI for the book in our triple-store, and
>> can make use of it to retrieve further information.
>>
>> Regards,
>>
>> Mark
>>
>> On 13/06/07, Ben Adida <ben@adida.net> wrote:
>>
>>
>> Cedric,
>>
>> This is an interesting question. I had to deal with this with the  
>> RDFa
>> clipboard [1], and I chose to use the predicate rel="rdf:li" on any
>> bnode I wanted to appear on the page, effectively saying "this  
>> bnode is
>> an item of the current page." For example, in your code below:
>>
>> <span class="foaf:Person" rel="rdf:li">
>> some things about the person
>> </span>
>>
>> which yields:
>>
>> <> rdf:li
>>      [a foaf:Person; ...things about the person...]
>>
>> I'm pretty sure this is not a "best practice", but it's the work- 
>> around
>> I came up with for precisely this issue, and it's not all that  
>> wrong in
>> terms of semantics: after all, that *is* an item on the page.
>>
>> -Ben
>>
>> CÚdric Mesnage wrote:
>> > Hi all,
>> >
>> > I have a question regarding blank nodes in RDFa, I don't know if  
>> the
>> > issue has been raised already and I apologize if it has. In the  
>> RDFa
>> > Primer I saw that you can create unnamed blank nodes using the  
>> 'rel'
>> > attribute as in the example:
>> >
>> > <dl class="foaf:Person" about="#card" id="card">
>> > ...
>> >  <dt>Address</dt>
>> >  <dd rel="foaf:address">
>> >   <span property="foaf:address_line_1">77 Massachusetts
>> Ave.</span><br />
>> >     <span property="foaf:address_line_2">MIT Room
>> 32-G524</span><br />
>> >   <span property="foaf:city">Cambridge</span> MA 02139<br
>> />
>> >   <span property="foaf:country">USA</span>
>> >  </dd>
>> > ...
>> > </dl>
>> >
>> > This works for predicates layered in an instance definition, do  
>> you plan
>> > having a similar principle for classes? I'd like to have:
>> >
>> > <span class="foaf:Person" >
>> > some things about the person
>> > </span>
>> >
>> > to be considered as a blank node, currently in RDFa On
>> > Rails(http://rdfa.rubyforge.org/) I generate blank node names  
>> this way:
>> >
>> > <span class="foaf:Person" about="#BNode1">
>> > some things about the person
>> > </span>
>> >
>> > incrementing the number through the page generation, but this is  
>> ugly.
>> > The other solution is that I can just forbidden the use of  
>> classes if no
>> > uri or explicit blank node name is given.
>> >
>> > Hope this does make some sense and look forward to get you point  
>> of view.
>> >
>> > Best Regards!
>> > ---
>> > CÚdric Mesnage
>> > PhD Student
>> > cedric.mesnage@lu.unisi.ch
>> <mailto:cedric.mesnage@lu.unisi.ch>
>> > http://www.inf.unisi.ch/phd/mesnage/
>> > http://myunderstanding.wordpress.com/
>> >
>> >
>>
>>
>>
>>
>>
>>
>>
>> --
>>  Mark Birbeck, formsPlayer
>>
>>  mark.birbeck@x-port.net | +44 (0) 20 7689 9232
>>  http://www.formsPlayer.com |
>> http://internet-apps.blogspot.com
>>
>>  standards. innovation.
>>
>
>
> -- 
>  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 15:02:31 UTC

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