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RDF: I fought the markup

I spoke with a colleague of mine yesterday. He's working with XUL/Mozilla at the moment. His least favourite bit? The RDF/XML. Hates it. Since he knows I'm an RDF fan, he rightly wonders what could I see in it. So... here's a six year old markup language, that started with three syntactic forms all lumped together; that was an early testbed for how to use namespaces; whose opportunity for real development in the W3C was hamstrung by its charter (and yet, while equally constrained, the model was rewritten from the ground up). Even its own working group didn't use it.

I gave him a thirty minute run down on RDF (and inevitably, RSS) history, explaining as best I could how we got here and why some of us think the RDF metadata has a lot to offer. I outlined some of the key thinkers behind it, early considerations as a syndication and device profiling format (my colleague, like a number people in Propylon, really understand the issues around device/phone profiling); why it's a good thing not to just have property-value pairs, but to explicitly name the thing that is being associated with the property; that we can enable stuff like third party distributed metadata, have precise definitions for properties, types and classes; that we can use it to help unify disparate data sets; that we can create and merge rich data graphs by using URIs as identifiers; that we can simplify data management and interchange; that we can think about extensibility in data as well as modularity; that in a pinch, we can fire up wget and see if a URI has any documentation. That in the long run, since RDF has a formal model, we can inference and query over data sets just we do with SQL, while unshackling the data from the database and maybe alleviating the extreme autism we see in relational data today. But for the syntax, I had no good answers or justification for sticking with it. The world is not overflowing with RDF/XML, and there is minimal (if any) infrastructure built on it. And as he astutely pointed out, the triples under the hood are meant to be preserved during transformation - indeed, that's the whole point.

Today, I ran across a post from Leigh, from last year, on Dorothea's RDF syntax rant:

Her posting made me wonder whether this frustration is down to the basic elements of the RDF syntax, e.g. the element and attribute names, or it's inherent variability: that there are multiple ways to encode the same data using slightly different syntactic structures.

I'm guessing -- and I'm hoping Dorothea will step in to correct me here - that most of frustration is because of the variability. That's certainly the cause of much griping from hackers keen to use plain old XML tools on RDF data. The variability defeats any attempt to use, e.g. XSLT, without an initial normalization step. - Leigh Dodds (RDF Syntax: Profiling and Styling)

Variability is only part of it. No-one I know can write it down without making mistakes, no-one I know can read it without getting confused. But people are expected to believe after coming into contact with RDF/XML, that RDF is really quite simple. And that the tools will save them.

But this doesn't mean that we have to throw out the syntax entirely.

I think we should consider throwing it out. The model was thrown out without anyone batting an eyelid. The syntax has been around for over half a decade - it's not catching on and I remain convinced that nothing hurts RDF adoption more than RDF/XML. Perhaps most damning, it's completely failed the dogfood test - if the W3C won't use the markup they're specifying, why would they expect anyone else to?


April 16, 2004 09:19 PM

Comments

Asbjrn Ulsberg
(April 17, 2004 01:11 AM #)

This is so pinpoint in the bulls eye that it's hard to describe how much I agree with you. Therefore, I just reply with the allmighty "AOL", and say "thanks" for the lovely article.

Alexander
(April 17, 2004 06:34 AM #)

Amen. Just a few days ago I threw my arms up in anger over the model (http://shelter.nu/blog-078.html), and RDF:XML doesn't make things better; I've rambled about this before. I come from the Topic Maps side of the world, really wanting to have an RDF channel for webifying my TM based maps, but ... I have to re-write all my tools, making it ... not really worth it. W3C needs to eat its own dogfood and do it well; if not, cancel the darn thing, and start again with a slightly smarter design. Please.

Asbjrn Ulsberg
(April 17, 2004 09:51 AM #)

This is probably a incendiary torch, but here goes: As Topic Maps aren't adopted half as much as they should, and not even close to a fraction as known and used at much other web technology, I don't find it very sad to see the existing TM go, and then the emergence of a new One True Metadata Format (maybe it should be called OTMF? ;-) which has the best from both RDF (which probably is mostly that it comes from W3C) and Topic Maps.

I find the current TM model, and not to mention syntax, much cleaner, better thought out and defined than RDF, but I find it very unlikely that W3C will ever just embrace the current standard as is, so they need to get a saying if the two formats were to become one.

I think Topic Maps and RDF have such big problems in getting accepted and adopted (RDF because of the horrific syntax, Topic Maps because they don't come from W3C) that they both would profit from merging into one format, and I as a developer certainly don't scream the more, the merrier.

If someone has trouble swallowing the allegation Topic Maps aren't popular because they don't come from W3C, just have a look at RelaxNG vs. XSD. RNG has a wildly more welldefined and simple model, but as XSD is a W3C brand, it's ridiculously more popular than RNG. Ok, Microsoft is very much to blame for the success of XSD, but that could also be the position with RDF if they adopt it. Just to be a bit blunt: I think Microsoft is much more open to W3C's standards, than standards coming from elsewhere.

Dorothea Salo
(April 20, 2004 01:32 AM #)

Where is XSD popular? I'm not seeing it. And I am seeing some fairly high-profile adoptions of RNG (e.g. OpenOffice, TEI).

Between you, you and Leigh have captured most of my chequered experience with RDF. (I didn't see Leigh's post when he first wrote it, for some reason.) All I would add off the top of my head is that Leigh's syntax profiles are a fine idea -- and in fact that's where the working group I mentioned was going -- but what good are they if RDF authoring tools don't respect them?

Which, AFAIK, they don't.

bryan
(April 20, 2004 06:12 PM #)

XSD is 'popular' (if we can remove from popularity the concept of being liked, and leave it with just being used) in the Microsoft world, and with companies that have resigned themselves wholeheartedly to doing whatever Microsoft says they should do.

I could also make some very snarky statements now about its popularity and draw conclusions as to why it is popular among certain folks, but to do so would probably seriously hamper my future employment opportunities. So I would say that XSD also seems to be relatively popular in large governmental projects, and again, although not liked, among web service proponents (if by web service we mean soap services, the services that take long to implement and generally don't work anyway, among them it's popular.)

Bill de hra
(April 20, 2004 07:06 PM #)

[[[
So I would say that XSD also seems to be relatively popular in large governmental projects..
]]]

Not in this one: http://sdec.reach.ie/

;)

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