Re: RDFa reliance on namespace declaration

[Ian Davis]

On 14/06/2006 13:48, Misha Wolf wrote:
Hi Ian,

Good point.  NewsML 2 has also taken your approach #2.  What syntax 
is eRDF using for this?

eRDF uses a convention that I first saw described in a W3C workshop 
report from 1996 [1]. This was later adopted for the Dublin Core[2].

Basically a schema prefix is declared in the head of the document like this:

<link rel="schema.dc" href="http://purl.org/dc/elements/1.1/"; />

That sets up the 'dc' prefix to map to the specified URI

In eRDF you can refer to that prefix in class attributes like this:

<div class="dc-title">

or

<div class="dc.title">

Both of which denote the http://purl.org/dc/elements/1.1/title property URI

The particular choice of delimiter (hyphen or dot) was arbitrary. The 
historical documents mentioned above use dots but when I wanted to 
extend it to work in the body of the document I added the option of a 
hyphen since dots have a particular meaning in the XHTML binding of CSS.

I did consider making it configurable, e.g. allowing

 <meta name="erdf.delimiter" content=":" />

But decided against the added complexity. Not that it would be hard to 
implement but it's another convention for humans to learn.

Anyone looking for an intro to eRDF might be interested in the 
presentation I gave at XTech this year:

http://research.talis.com/2005/erdf/xtech2006.html

Ian

[1] 
http://www.w3.org/Search/9605-Indexing-Workshop/ReportOutcomes/S6Group2.html
[2] http://www.dublincore.org/documents/dcq-html/

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