your SW piece

Hi Clay,

I've been following the discussion around your recent 
piece on the Semantic Web. I dropped a few comments into 
weblogs here and there([1]) since your site doesn't have 
a comments facility, but thought I'd send you a quick note 
too.

It's always interesting to see how others perceive these things. 

The main thing that struck me was how the logical rules 
/ formal inference side of Semantic Web dominates your 
perception of what we're trying to achieve with RDF 
and related technology at W3C. You're certainly not 
alone in that; many of the KR/AI crowd 
have got involved, and several of my colleagues here at W3C 
certainly find that aspect of the technology quite 
compelling. However if you look at the work we've been 
doing, particularly around the core RDF specs[2] I think 
you'll find much of it reassuring near-term in scope. Since 
your piece is couched explicitly in terms of W3C's work, 
I was dissapointed that you missed out on this. Many 
RDF apps get by perfectly well without any fancy 
inference rule machinery, exploiting the RDF data model 
as a handy mechanism for mixing independently created 
data vocabularies.

The Semantic Web project, viewed as an effort to make it 
easier to publish, mix, share and consume data on the Web, 
depends on logic in pretty much the same way SQL or UML
depend on logic. Creating an RDF vocabulary (ontology, etc)
involves making a number of pragmatic tradeoffs, between 
predictability (nice tidy categories) versus real world 
messyness. These tradeoffs are familiar to database 
designers the world over, and not peculiar 
to the SW effort. One point I was particularly puzzled by 
-- perhaps you could help me out here -- was your 
apparent impression that we're working towards a single, global, 
monolithic ontology. 

The reality of SW hackerdom that I'm familiar with 
is quite the opposite. There are a number of 
evolving RDF vocabularies, each of which describes some 
part of the puzzle in a level of detail, and from a perspective, 
appropriate to the needs of those creating it. If it works 
for others too, in part of whole, that's great. If not, there's 
plenty of room for another perspective in the SW vocabulary 
marketplace([3]). In this regard, the SW to me feels 
reassuringly bottom-up, grassroots led (eg [4]); a characteristic 
that stems from the technical design of RDF. 

Unlike vanilla XML, RDF vocabularies can be freely 
mixed together in data without prior agreement. So 
you often see ad-hoc combinations of Dublin Core, 
RSS1, MusicBrainz, RDF-calendar, FOAF, Wordnet, 
thesaurus, Geo-info etc etc frequently deployed together, 
despite the fact that the creators of those various 
vocabularies barely knew each other. This strikes me as the 
height of loosly-coupled pragmatism rather than a 
wide-eyed effort to build a monolithic universal category 
system. But if this is they way our project looks from 
the outside, it is good to know!

I had a few more comments in [1] regarding the Friendster 
mention towards the end of your article. I think you 
missed a point here. SW technology allows, but by no 
means requires, people to make simplistic over-generalisations.
My own experience with FOAF is that lots of people do want to 
exchange data that embodies sweeping and simplistic generalisations
about subtle social relationships. But you can make such mistakes 
on any platform (see various SQL-backed social networking sites for details).
SW technology, specifically RDF, makes it *possible* to goof up 
in various ways, but it also allows for subtler treatments, which 
is where (hopefully) FOAF is headed through its focus on 
describing the photos, events, collaborations etc that are the 
evidence friendship leaves in the world, rather than crudely 
taxonomising classes of friend. So, again, it felt like a strawman 
was being punished in those observations. 

From where I'm stood, the SW project is all about getting RDF 
descriptions of things deployed in the public Web. The 
vocabularies that support those descriptions (ontologies) 
come from a variety of sources, adopt varying tradeoffs, and 
-- inevitably -- overlap in scope and coverage. What we have 
created in RDF, I believe, is a framework for allowing these 
ways of describing the world to compete in a way that lets 
application developers adopt a fine-grained approach to 
using them. This is a technical characteristic of RDF which 
counts against the 'global ontology' concern you raise: RDF's 
design makes it easier to pick'n'mix pragmatically from 
various pre-existing vocabularies, adding in extensions and 
qualifications of your own where needed.

Hmm OK this was supposed to be a short reply! I'll copy it 
to www-archive@W3.org so it'll show up in 
http://lists.w3.org/Archives/Public/www-archive/ -- if you've 
time to respond, copying www-archive will similarly put your 
reply in Google-able space.

(Short version of this might've been: there's more to the SW 
than rules and inference...)

cheers,

Dan



[1] http://dannyayers.com/archives/002016.html#comments
[2] http://www.w3.org/RDF/
[3] http://esw.w3.org/topic/VocabularyMarket
[4] http://www.xml.com/pub/a/2001/07/25/rdfcalendar.html

Received on Monday, 10 November 2003 17:38:52 UTC