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Re: GRDDL and OWL/XML

From: Bijan Parsia <bparsia@cs.man.ac.uk>
Date: Sat, 10 May 2008 00:39:37 +0100
Message-Id: <C43C8395-A1ED-4B51-B875-5A8335F9E2D1@cs.man.ac.uk>
Cc: public-grddl-wg@w3.org, public-grddl-comments@w3.org
To: "Chimezie Ogbuji" <ogbujic@ccf.org>

On 9 May 2008, at 23:24, Chimezie Ogbuji wrote:

> On 5/9/08 5:07 PM, "Bijan Parsia" <bparsia@cs.man.ac.uk> wrote:
>> I can't seem to subscribe to the group, thus I cannot easily discuss:
>> http://lists.w3.org/Archives/Public/public-grddl-wg/2008May/0001.html
>> http://lists.w3.org/Archives/Public/public-grddl-wg/2008May/0002.html
>>
>> Please specify the appropriate venue
>
> public-grddl-comments?

Ok, I've subscribed and hereby redirect this conversation there, if  
that's alright. Note the replyto.

I would like to set some ground rules for the debate. Obviously I  
have no *power* to foist these on anyone, but if things go too far  
from these I probably will withdrawal from the conversation.

First, please presume that I've looked at the GRDDL spec with some care.

Second, please presume that I have a pretty wide experience with the  
W3C (including non-semantic web working groups).

Third, please presume good faith on my part. I'm not out to cast bombs.

Fourth, please recognize that I've just come from a working group  
fight where pure procedural tactics were thrown against me in an  
effort to squash my perspective. (Note, I'm not attributing malice  
here! I think there was genuine misundestanding. But the *effect* is  
that I was made to feels that my substantive arguments and concerns  
just didn't count.) So I may be a bit touchy, but also that I've  
worked out my position in some detail. I would be surprised if there  
is an easy peasy refutation.

That I feel the need to say all this is some indication of the  
situation.

>> Note that I do not believe that "leaving it to the reader" is really
>> the best characterization of my views. I won't go into detail until
>> we settle on a proper forum, but I believe that my approach is
>> compliant with the GRDDL spec and is appropriate for the
>> circumstances and that providing XSLT (in this circumstance) is an
>> anti-pattern on many levels (I would say this of POWDER too,  
>> actually).
>
> How is use of XSLT an anti-pattern?

So, first, let me emphasize that I say this very specifically for the  
situation of OWL/XML and (I suspect) POWDER. And I really mean that I  
think it's, by strong default, wrong for a W3C working group to  
provide as a normative or informative deliverable a namespace  
document which points to an XSLT *or any other implementation of a  
GRDDL transformation function* in such a way that GRDDL processors  
will, automatically, use that implementation. This is an overridable  
default, but a strong default, IMHO.

I feel fine in asking a W3C wg to provide a specification *for the  
transformation function*, but it should not be the presumption that  
saying "Support GRDDL" means providing an implementation.

I will argue both against the doing and the presumption.

First against the presumption: The GRDDL spec, afaict, requires  
nothing more that the specification of a transformation function and  
an identifier for it. That is how I read the spec and, during the OWL  
WG charter debates, how I represented the requirement for "GRDDL  
support". There's a big difference between requiring a spec for a  
transformation and requiring an implementation thereof. I believe  
other people outside the GRDDL community can feel like they were  
shanghaied into something they really didn't expect to have to do.  
This means that the reflex will be to resist any GRDDL requirements  
or requests altogether (which is certainly where I'm leaning now).  
So, just tactically, I recommend allowing and encouraging the lighter  
path. My understanding of the spirit of GRDDL was *not* to be  
intrusive. Requiring people to produce, or even to bless, an  
implementation is rather intrusive.

(In this particular case, it directly burdens me and my organization.  
We have fairly unique expertise in this transformation and, I've  
found, that I often get called on by the group to do this sort of  
work. Given that my org has a competing product, e.g., <http:// 
owl.cs.manchester.ac.uk/converter/restful.jsp>, I trust you  
understand why this is more than a little odd and unpleasant.)

Against the implementation requirement.

1) The primary purpose of W3C working group is to produce  
specifictations...standards, in fact. Many members of the W3C (who  
pay fees, after all) are implementors and vendors of implementations.  
The W3C, itself, enjoys a great deal of prestige and attention that  
its smaller members cannot hope to compete with. Futhermore, the W3C  
has a monopoly of W3C web space. Thus, it has a monopoly on what  
implementations it not just recommends, but *delivers* to people (via  
GRDDL agents). This makes it very difficult to compete with that  
implementation. Since WGs generally don't live very long, things  
stagnate (i.e., the W3C doesn't generally have the resources to  
maintain *lots* of software).

Furthermore, building or evaluating implementations is not well done  
in a WG. The time is constrained and there are many demands. It's a  
committee of people working part time. Software development is hard  
and blessing requires *at least* QA. The W3C generally doesn't  
provide test suites sufficient for QA, or even for interoperability  
testing and doesn't purport do (indeed, often purports explicitly  
*not* to).

2) I believe that GRDDL with web based XSLT shines in cases of  
*distributed* extensibility. In the radical case, I know something  
specific about an xml document I've thrown together and want to  
provide a "semantic stylesheet" for it (perhaps overriding the  
default semantic stylesheet). However, with W3C specs, we are engaged  
in *centralized*, global extensibility. Indeed, members pay a lot of  
money (not just fees) to do this.  (see <http://www.w3.org/2008/Talks/ 
0421-ac-tbl/> slide 9. I think the analysis is wrong here, or at  
least too simple. It's not *just* size, it's size + uptake +  
coherence + available infrastructure. Smaller communities can  
perfectly get away without URIs if they control most of the tools or  
tool builders/authors can't help but find the community norms).

I don't think it's a real burden on GRDDL implementors to find or  
write a translation implementation from OWL/XML to OWL/RDF. If  
someone provided a production quality XSLT, the GRDDL implementors  
could just download it and bundle it. Indeed, I would hope that  
quality GRDDL implementation would allow users to configure their  
client for offline or variant use (e.g., using XML Catalog).

There is a strong, large, and vocal community which is against  
putting key parts of implementations of global consensus specs on the  
web with the intention that it be downloaded and used by  
implementations. (I'm clearly a member of that community :)) Here is  
one explication of this line:
	http://hsivonen.iki.fi/no-dtd/
Everything there applies to GRDDL XSLT (or other implemention).

3) When you have a normative spec for a transformation function (as  
OWL does), adding an XSLT sets up a 'second variant' of the spec (as  
well as being a blessed implementation) and one that gets directly  
used in spite of it being nominally informative. This is a violation  
of DRY (don't repeat yourself) and divides attention from verifying  
the actual spec (e.g., with multiple implementations). Worse, bugs in  
the program become part of the de facto spec.

Ok, running out of steam. This is definitely more than enough to get  
started :)

Cheers,
Bijan.
Received on Friday, 9 May 2008 23:37:43 GMT

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