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Re: Understanding why RDFa is useful

From: Ian Hickson <ian@hixie.ch>
Date: Fri, 2 Jan 2009 08:18:47 +0000 (UTC)
To: Charles McCathieNevile <chaals@opera.com>
Cc: "public-html@w3.org" <public-html@w3.org>
Message-ID: <Pine.LNX.4.62.0901020750551.25317@hixie.dreamhostps.com>
On Fri, 2 Jan 2009, Charles McCathieNevile wrote:
> I think it would be helpful for people who are on this list, but don't 
> happen to follow WHATWG, to provide use cases [for using RDFa].

Indeed. The e-mail that Charles is referring to is:


...which may help guide the conversation.

> In particular, identifying things that RDFa does which Āµformats don't, 
> (such as provide a unified parsing method for arbitrary data that 
> enables it to be combined without a priori knowledge of the model behind 
> the vocabulary) and explaining what use cases that serves which would 
> not be met by existing mechanisms, is probably the clearest way to 
> determine the benefits RDFa could offer.

Note that it's not so much the benefits that RDFa could offer that are 
helpful, so much as the problems that exist that people think we should 
solve (that RDFa, amongst other technologies, might address).

In particular, as with the arguments for headers="" or summary="", it's 
important to not assume that we should have RDFa and try to find a reason 
for it -- maybe RDFa isn't the best way to solve the problems and 
requirements and use cases put forward, or maybe it is a way to solve some 
but not others, or maybe it solves more problems than we set out to solve. 
All of these possibilities exist, and so it's important to not assume the 
solution in the statements of the problems.

Similarly, in requirements we have to be careful not to assume solutions. 
So for example, Charles suggested the following requirement in his e-mail 
to the WHATWG list:

| Since many people use RDF as an interchange, storage and processing
| format for this kind of data (because it provides for automated mapping 
| of data from one schema to many others, without requiring anyone to 
| touch the original schemata or agree in advance how they should be 
| created), I believe there is a requirement for a method that allows 
| third parties to include RDF data in, and extract it from information 
| encoded within an HTML page.

If the goal is to use a widely used format, then the requirement should 
say "we must be compatible with a widely used format", or some such, and 
then we should look at data to find out what the widely used formats are. 
We shouldn't jump to assuming that RDF is part of the solution.

(Equally we shouldn't jump into the assumption that SQL, or CSV, or any 
data format at all is part of the solution.)

The reason I mentioned RDFa in the thread on the WHATWG list is that 
someone asked if we could add RDFa, and so the question, as with any 
request for a feature, is "what problem does this solve?".

> Ian has started a thread on the WHATWG list (but not here for some reason)

I didn't start it, I was responding to a thread started by Matt Bonner on 
the WHATWG list last August. I reply to threads in the same list as they 
are sent.

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Friday, 2 January 2009 08:19:30 UTC

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