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Re: Practical relevance (e.g., Re: GRDDL and OWL/XML)

From: Harry Halpin <hhalpin@ibiblio.org>
Date: Tue, 20 May 2008 12:09:30 +0100
Message-ID: <4832B16A.9000206@ibiblio.org>
To: Bijan Parsia <bparsia@cs.man.ac.uk>
Cc: "Booth, David (HP Software - Boston)" <dbooth@hp.com>, "public-grddl-comments@w3.org" <public-grddl-comments@w3.org>, "public-grddl-wg@w3.org" <public-grddl-wg@w3.org>

Bijan - again, it's pretty clear with movement by Yahoo!  and the rapid 
spread of microformats like XFN that GRDDL-like mechanisms are taking 
off. Of course, Yahoo are using their own mechanisms and not GRDDL per 
se. However, having quick, auto-discoverable and easy ways to get RDF 
out of certain XML formats is useful for people or clients that do not 
want to locally code transforms for every vocabulary they might 
encounter. I would look at Brian Suda's successful use of getting iCal 
and vCards out of microformats as a good use of how GRDDL could work in 
the future [1].

The concrete use-case for GRDDL is rather simple. There might be 
GRDDL-aware RDF-enabled clients that do not natively transform OWL2. If 
so, at least one GRDDL transform in a widely deployed format like XSLT 
helps them. If you do not think that is likely, that's fine. However, 
that is just a difference of opinion between us at this point, and 
again, the OWL2 WG should decide as a whole.

 I am glad that the argument has moved away from the idea of having a 
non-executable GRDDL to use-cases, and there is a use-case document that 
you may want to look at  [1]. Again, as GRDDL transform link in RDF in 
the namespace doc are not human-readable, there's as much sense there as 
counting an OWL2 reasoner an algorithm "implemented" in an academic 
paper available only in PDF. It would make sense to have a human+machine 
readable link to all implementations from the namespace document using 
RDDL. I do not see any use case for a non-executable machine-readable 
link. That argument does appear to be odd to me and many others, moreso 
than the use-case outlined above for GRDDL.

Bijan Parsia wrote:
> It would be good to have an answer to:
>     http://lists.w3.org/Archives/Public/public-html/2008May/0102.html
> """In practice it isn't at all clear that GRDDL is in any way relevant 
> in the
> real world (much like almost anything related to RDF), and so it isn't
> really an important concern for the development of the HTML language."""
Again, see movement by Yahoo. Some people are interested in RDF. If HTML 
5 has a XML serialization (which it will) then it will be much easier to 
"GRDDL" out of existing HTML 5. It's a chicken and egg problem.
> Granting that this is a hostile audience ("much like almost anything 
> related to RDF") I really would like to know an answer. OWL/XML seems 
> to be about the best case one could hope for (since OWL/RDF *is* 
> something we want), but it's really hard to say why GRDDL (in the 
> sense of autoexecutable) is remotely relevant. It doesn't *enable* any 
> functionality; it merely mandates a certain *style*.
> Can we have some scenarios? Concrete ones? I've spent time trying to 
> think of one, but I really have trouble. Even in the OWL case.
> I've heard in the OWL case, for example, that OWL/XML risks shutting 
> out legacy tools that only consume RDF/XML. But first, they don't seem 
> to be GRDDL sensitive anyway (e.g., Protege3.x). Second, there are 
> plenty of ways to get RDF/XML from OWL/XML that are easily 
> discoverable (e.g., 
> <http://owl.cs.manchester.ac.uk/converter/restful.jsp>). It seems like 
> users of legacy OWL tools have *plenty* of mechanisms to work with 
Why is that easily discoverable by the end-user? A GRDDL transformation 
is equally easily discoverable.
> Ok, let me try another: semantic web spiders (swoogle etc.). If 
> there's GRDDL available they'll be able to scrape more and more easily.
> But this *also* seems strange. If I'm a spider author, I'm going to 
> make damn sure that my translations are robust (or I'm just writing a 
> toy and it seems catering for toy tools is very strange). So what I 
> want is the clearest possible specification of the translation. This 
> will almost surely not be an XSLT (for example) except in the 
> simplests of cases. (And qua spec, a pdf of the XSLT is fine.) I mean, 
> however does Google *manage* being able to search Word docs and PDFs 
> and so on without GRDDL like translations available for them to download?

Again, GRDDL does not mandate XSLTs and other types of executables are 
possible. If one did not have a *finite* number of vocabularies, but 
just wanted to scrape as much RDF as possible, then GRDDL could be used.

> Ok, here's a final scenario, suppose I have a generic RDF web browser, 
> call it Fabulator. To be, in abstracto, maximally useful it needs to 
> be able to get maximal amounts of RDF from sources (let's suppose). 
> So, autoGRDDL helps, yes?
> This seems almost plausible, though not for the OWL case (since that's 
> well known and all the arguments in spidering apply), but again, if we 
> look at the web, we see no autoloading, but always with user 
> intervention, typically directed back to the *browser author* site, 
> not to the namespace.

See spidering argument.

> I do see a use for having a "GRDDL" tool, that is, something that can 
> scrape various formats (but not just XML? see the first part of 
> Hixie's email) to RDF *for the RDF person*. (And sometimes, I am that 
> person!) And I'd like format authors, when it's reasonable, or at 
> least, format communities, to provide a preferred way of doing the 
> translation *so I can update my tool*. I don't want to *force* them to 
> spec it "on spec" so to speak (e.g., how many people *pay* for RDF 
> functionality, either in cash or in fame and fortune and 
> connections?), but it seems like one could be judicious and friendly 
> about it.

Again, GRDDL can be enabled or disabled by local policy, i.e. 
command-line settings, etc. Again, the idea behind GRDDL is to get RDF 
out of commonly deployed formats. We do hope that OWL2 XML would be one 
of the commonly deployed format.

> Cheers,
> Bijan.
[1] http://suda.co.uk/projects/X2V/
[2] http://www.w3.org/TR/grddl-scenarios/
Received on Tuesday, 20 May 2008 11:10:18 UTC

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