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Re: The war of the worlds: HTML vs. RDF

From: Tom Morris <tom@tommorris.org>
Date: Fri, 9 Jan 2009 19:27:42 +0000
Message-ID: <d375f00f0901091127m362cad08vc544bb9c6a8f4538@mail.gmail.com>
To: "Justin James" <j_james@mindspring.com>
Cc: "Giovanni Gentili" <giovanni.gentili@gmail.com>, public-html@w3.org

On Fri, Jan 9, 2009 at 18:15, Justin James <j_james@mindspring.com> wrote:
> Why not allow a "Semantic Style Sheet" to allow the external (to the HTML
> document) construction of semantic classes/IDs/etc., and allow any HTML
> element to have a class/ID/etc. attribute, that ties back to the style sheet
> referenced in the page's HEAD section? In other words, leverage the
> knowledge that authors already have with CSS, and simply give them the
> ability to use RDFa just like they already use CSS? Why do we need to add
> new tags or *force* them to re-specify semantics on a per-tag basis (using
> the "semantic" attribute that you propose)? This should work precisely like
> CSS, but with semantics. And ARIA should be involved along the way too.

You can do that already with HTML 4 and XHTML 1.x using GRDDL. GRDDL
no longer works in HTML 5 as the profile attribute has been removed.
(We get some nonsense about GRDDL still working but just not
'requiring' profile. This is nonsense. It's a bit like saying that
you've taken the wheels off the car but it still works because you can
turn the engine on.)

The current plan for GRDDL is that for HTML 5 you can put the profile
URI in a link element with rel="profile". By the time that HTML 5
becomes widely used, I'm sure we'll be able to fix up the GRDDL
implementations to support that. What's that principle called - break
existing implementations?

> To be frankly honest, 90% of the problem here is the RDFa spec. It reads
> like stereo instructions. Raise your hand if you honestly think that the
> average HTML author understands what the word "tuple" means. On top of that,
> RDFa is this completely unpublicized spec. I never even heard of it until I
> was on this list for a few months, and I have been a "real world Web
> developer" (I build Web sites, not Web browsers, I don't spend my nights
> reading IETF drafts, I've never met Tim Berners-Lee, etc.) for a long time
> now. So unless the RDFa folks a) make their draft useful to real-world
> people, b) evangelize their work, c) provide some useful tools for RDFa, and
> d) provide some real world use cases that the average developer will say,
> "hey, this makes my life easier!", this is a non-starter.

Criticising RDFa on the basis of a complex spec is rather silly. All
technologies have complex specs. There's no way your average
DreamWeaver or FrontPage user can get their head around the HTML spec
(either 4 or 5) - this is why there are tutorials and other reference
works. From the perspective of the implementer, the RDFa spec is
pretty well-defined, and the audience of the RDFa spec (like most
specifications) *is* implementers (I'm in the middle of implementing
RDFa and have implemented RDF/XML, and both have been pretty easy to
implement, and come with excellent test suites).

For those who aren't implementing RDFa, there is plenty of material
online to guide them how to use it. The RDFa Primer is published by
the W3C <http://www.w3.org/TR/xhtml-rdfa-primer/> and there are also
lots of other materials you can find by Googling.

As for examples of RDFa in use, the UK Government's official journal
of record, the London Gazette (established 1665!) now publishes their
data as XHTML+RDFa. See

Tom Morris
Received on Friday, 9 January 2009 19:28:23 UTC

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