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From: Ed Summers <ehs@pobox.com>
Date: Mon, 26 Nov 2007 14:08:49 -0500
Message-ID: <f032cc060711261108w66dfcebbq657b62c48e5b3fdd@mail.gmail.com>
To: public-sweo-ig@w3.org

On behalf of the Semantic Web Deployment Working Group I reviewed the
semweb-faq [1] in light of SKOS. I have a few suggestions which I've
included below with a bit of commentary. Please feel free to use
whatever is useful in these suggestions.

I also crafted a short answer to a question "What is SKOS?"--which was
largely pulled from a recent writeup of SKOS & RDFa by Alistair Miles
[2]. Alistair has given his approval for the text to be used if you
think it would be helpful to directly address SKOS in the faq.

Thanks for asking for our input on this very useful document!



... Must I use ontologies for Semantic Web Applications?

"These different technologies differ in expressiveness but also in
complexity: applications have a choice (RDF Schemas represent the
simplest ontology level, OWL Full being the most complex one, SKOS
when less rigorous terminologies, glossaries, are to be used, etc).
They also have a choice of not to use any of those; the usage of
ontologies is not a requirement for Semantic Web applications."

I think it's important to encourage people to reuse ontologies before
creating their own, and SKOS is a good example of a re-usable
ontology. So here is some slightly modified language.

These technologies differ in expressiveness but also in complexity.
Applications have a choice along a range from RDF Schema for
representing the simplest ontology level, to OWL Full for maximum
expressiveness. In addition semantic web users are encouraged to
leverage existing ontologies where possible: e.g. SKOS for
representing basic structures like thesauri, taxonomies or other
controlled  vocabularies. Good places to look for existing ontologies
are detailed elsewhere in this FAQ [3].


... tagging, folksonomies

"While tagging is easy and somewhat useful, it destroys a lot of the
semantics of the data. In the Semantic Web, instead of tagging data
items with strings, they can be related to other resources which can
be uniquely identified, like ones representing people and places. The
relationships are very specific, like who took the photograph, who is
in the photograph, where the photograph was taken."

It seems to me that the semantic web community is beginning to see
that folksonomy and tagging may have a role to play in the semantic
web. For examples of this see flickrwrapper at dbpedia [4] and
Alistair Mile's latest thinking on SKOS [2]. I think it would serve the
semantic web effort well by encouraging this collaboration rather than
dismantling it. So here's a rephrasing of the above:

While tagging is easy and somewhat useful, it often destroys a lot of
the semantics of the data. A folksonomy tag is typically 2/3 of a RDF
triple. The subject is known: e.g. the URL for the flickr image being
tagged, or the URL being bookmarked in delicious. The object is known:
e.g. http://flickr.com/photos/tags/cats or
http://del.icio.us/tag/cats. But the predicate to connect them is
often missing. Machine-tags [5] lend themselves to RDF more since they
better capture the relationship between the subject and the object.
Folksonomy providers are encouraged to capture or infer the semantics
around their tags and to leverage semantic web technologies such as
RDF and SKOS to publish machine readable versions of their concept


... What is SKOS?

The Simple Knowledge Organization System (SKOS) is an ontology for expressing
the basic structure and content of concept schemes such as thesauri,
classification schemes, subject heading lists, taxonomies, glossaries,
folksonomies, other types of controlled vocabularies. It provides a standard,
low-cost way of migrating existing concept schemes to the Semantic Web,
so that they can be used as-is for the development of lightweight Semantic Web
applications. SKOS is increasingly seen as a bridging technology, providing
the missing link between the rigorous logical formalism of ontology languages
such as OWL and the chaotic, informal and weakly-structured world of social
approaches to information management, as exemplified by social tagging

[1] http://www.w3.org/2001/sw/SW-FAQ
[2] http://isegserv.itd.rl.ac.uk/blogs/alistair/archives/84
[3] http://www.w3.org/2001/sw/SW-FAQ#findont
[4] http://www4.wiwiss.fu-berlin.de/flickrwrappr/
[5] http://www.flickr.com/groups/api/discuss/72157594497877875/
Received on Monday, 26 November 2007 19:08:59 UTC

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