Re: .htaccess a major bottleneck to Semantic Web adoption / Was: Re: RDFa vs RDF/XML and content negotiation

Hi Tom,

On Sun, Jun 28, 2009 at 11:46 PM, Tom Heath<> wrote:
> Martin,
> 2009/6/27 Martin Hepp (UniBW) <>:
>> So if this "hidden div / span" approach is not feasible, we got a problem.
>> The reason is that, as beautiful the idea is of using RDFa to make a) the
>> human-readable presentation and b) the machine-readable meta-data link to
>> the same literals, the problematic is it in reality once the structure of a)
>> and b) are very different.
>> For very simple property-value pairs, embedding RDFa markup is no problem.
>> But if you have a bit more complexity at the conceptual level and in
>> particular if there are significant differences to the structure of the
>> presentation (e.g. in terms of granularity, ordering of elements, etc.), it
>> gets very, very messy and hard to maintain.
> Amen. Thank you for writing this. I completely agree. RDFa has some
> great use cases but (like any technology) has its limitations. Let's
> not oversell it. put me in a difficult position here. :)

If I leap to RDFa's defence then it looks like I think it solves all
the world's problems.

But if I remain silent, then it looks like the problem being raised is
some kind of fundamental flaw.

Ah well, let's dive in...

First I should say that I'd be the first to agree that RDFa has
limitations. But the issue here is that I don't think the problem
raised by Martin can be classed as a limitation in the way you're
implying, Tom.

If we go back a step, RDFa was carefully designed so that it could
carry any combination of the RDF concepts in an HTML document. In the
end we dropped reification and lists, because it didn't seem that the
RDF community itself was clear on the future of those, but they are
both easily added back if the issues were to be resolved.

In short, it is possible to use HTML+RDFa to create complete RDF
documents, such as RDF Schemas, OWL ontologies, and so on, and the
resulting documents would be no more complex than their equivalent
RDF/XML or N3 versions, with the benefit that they can be delivered
using any of the many HTML publishing techniques currently available.

But most of the discussion around RDFa relates to its other use, where
it's possible to use it to 'sprinkle' metadata into HTML documents
that are primarily aimed at human readers. By being alongside the
human-readable output, it makes the metadata easier to maintain. And
in addition it gives the user agent the opportunity to enhance the
view of the data, by making use of the 'local' metadata.

However, the point that Martin was getting at, is that sometimes there
is just way more data in the 'RDF view' than in the 'human view', and
that makes it very difficult to make the two align.

I don't think that this is a flaw in RDFa itself, and I'm not
convinced that there is an easy solution in the form of another
technology that would solve this. Martin's solution seems a reasonable
one to me.

(Although I wonder if part of the problem might be that too much
information is being provided in the RDF view, rather than using links
to other data that can be retrieved. Perhaps Michael could give an



Mark Birbeck, webBackplane

webBackplane is a trading name of Backplane Ltd. (company number
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Received on Monday, 29 June 2009 12:31:02 UTC