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comment on using RDFa

From: Peter Mika <pmika@yahoo-inc.com>
Date: Mon, 28 May 2007 18:02:14 +0200
Message-ID: <465AFD06.4010905@yahoo-inc.com>
To: public-rdf-in-xhtml-tf@w3.org

Hi All,

I have some comments on RDFa based on my experiences in trying to use it 
for the openacademia project. Basically, the idea is to use RDFa to mark 
up publication metadata in HTML publication lists generated by 
openacademia. These typically are embedded in personal homepages as in 
[2]. We are using the SWRC ontology for publication metadata and FOAF 
for personal metadata.

My knowledge of RDFa is based on the Primer and I havent' followed the 
mailing list so far, so please forgive me if I point out something 
obvious or something that is already noted.

Comment #1

RDFa seems to interfere with existing markup. On the pages we generate 
we would like to have both our own markup, hCard as well as RDFa.

My first attempt to mix hCard and RDFa would be:

<span class="vcard">
    <span class="fn foaf:Person" property="foaf:name" 

This doesn't work: when I unleash the RDFa bookmarklet on this I get the 
nonsensical triple which says that #peter_mika is both type foaf:Person 
and type fn.

So the solution seems to be:

<span class="vcard">
    <span class="fn">
        <span class="foaf:Person" property="foaf:name" 

Still, the bookmarklet generates four triples:

<http://www.cs.vu.nl/~pmika/publications.bib#peter_mika> foaf:name 
"Peter Mika" .
<http://www.cs.vu.nl/~pmika/publications.bib#peter_mika> rdf:type 
foaf:Person .
<> rdf:type fn .
<> rdf:type vcard .

(The last two seem to be a bug?)

The fact that I cannot mix RDFa class names and other class names in a 
single span element makes things even more complex when I want to say 
that there is a publication and this person is the author of it. My 
current minimal solution requires six levels of nesting (!):

<li class="swrc:Article" 
        <span class="hbib article">
            <span class="vcard">
                <span class="author fn">
                    <span rel="swrc:author" 
                        <span class="foaf:Person" property="foaf:name" 
                            Peter Mika
             <!-- Next author would come here -->

Since this seems to defeat the purpose of human-writable markup, I 
suggest minimally documenting this issue... Stronger, I would have 
expected this to work based on the experiences with microformats, which 
happily mix together in the same class attribute.

Note that from this code the bookmarklet still produces a number of 
nonsensical triples involving the non-RDFa classnames.

Comment #2

It seems unnatural to put the foaf:Person class attribute on the element 
that gives the name of the person. However, when I try the seemingly 
logical solution:

           <span class="foaf:Person" rel="swrc:author" 
                        <span  property="foaf:name">
                            Peter Mika

What happens is that the publication becomes type foaf:Person, instead 
of #peter_mika. Again, this is unnatural to me, so I suggest to change 
it, or if this is the best possible compromise, then it would be helpful 
to document it to alert users.

Hope these comments are helpful... please let me know if I'm doing 
something wrong or have been misinterpreting how things should work.

Peter Mika
(Yahoo! Research Barcelona)

[1] http://www.openacademia.org
[2] http://www.cs.vu.nl/~pmika/research.html
Received on Monday, 28 May 2007 16:04:11 UTC

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