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Books & Articles I wrote.

Friday, April 28, 2006


RDF/A Primer

Karl Dubost pointed me at the RDF/A Primer 1.0 which is one or the more exciting documents i have seen in recent times.

Embedding RDF and XHTML has been around for a number of years, but it has always been left to the person adding the data to decide how they want to specify it. It has always been hard to get your average joe to add their contact information in some format that that si semantically readable, yet easy to do. This primer is a good start to narrowing that gap.

In effect it does what Microformats do, but leverages existing technologies such as FOAF - cementing the DRY principle in a global context.

You can specify data about yourself in the following way:

<li id="andrew" about="#andrew">
<link rev="foaf:member" href="" />
<span property="foaf:firstname">Andrew</span>
<span property="foaf:surname">Smith</span> can be contacted on
<span property="foaf:phone">+1 777 888 9999</span>

This is open and uses existing FOAF information which is nice.
The question now is whether to use this or Microformats. Micrformats has the advanage of things having a short well-defined meaning - hCard, hCalander and so on.

An example Microformat contact card example is shown below.

<div class="vcard">
<a class="url fn" href="http://tantek.com/">Tantek Çelik</a>
<div class="org">Technorati</div>

The RDF/A version is much more flexible in that it doesn't really what what kind of data you are adding or how to specifiy specific types of data - it leaves this to the creator. It can be interpreted by parsers who grok the namespaces used.

They certainly overlap - i just wonder whether Microformats that use RDF/A would work best. Or in reverse, if the RDF/A created a set of definitions that were well defined semantically.

e.g. "to create a contact card FOAF", "to create a calander, use rdf calander" and so on. It's not about limiting the flexibility - it's more about telling people who intend to create the data where to start and what to use, as the combination of XHTML and the various schemas out there (foaf, ical and so on) is very flexible.

This is what Microformats do well just now - they basically say, to create a contact card, use these and do this.

I have to say the RDF/A document is the most interesting to me as it is very extensible and uses existing tools. I'd just like to see "cut and paste" fragments for things such as "email and name", "home address", "education", "an event today" and so on - things that could be defined, populated and saved in no time at all.

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