[foaf-dev] Re: updated FOAF spec

Dan Brickley danbri at danbri.org
Tue May 29 12:24:41 BST 2007

Henry Story wrote:
> Oops sorry. I just realised on reading this thread more closely that 
> these relations exist in owl:
> owl:DeprecatedClass and owl:DeprecatedProperty
> Sorry.

No worries, we neglected them too in the FOAF scene.

I increasingly like the metaphor of RDF/OWL vocab as dictionary, and 
think this worth saying explicitly, to avoid the common default of 
thinking about these things are file or document formats. That mode of 
thought makes sense in XML, but with RDF, ... doesn't really. So I think 
a section of the "dictionary" for words that are ... "deprecated" means 
something like "if you go using these terms ... well ... here's what 
they are generally taken to mean ... but there are good reasons for 
trying to find another way of expressing yourself.". It might be 
interesting to enumerate (just in prose for now) some of the various 
reasons for deprecation, and see how the dictionary metaphor shapes up 
for each. For eg., Deprecated-"archaic", deprecated-"other vocab 
preferred", deprecated-"duplication", deprecated-"murky semantics", 
deprecated "nobody liked it or used it", etc.

> btw, one thing that I sometimes find missing when reading a spec is some 
> guidance as to which other ontologies play nicely with a given one. Some 
> ontologies are so minimal it feels like there are a number of missing 
> properties until one realises that one is meant to use a dc property for 
> example.

Yes, ... exactly! Sometimes "finding another way to express yourself" 
may mean using an alternate namespace/vocab instead. There are many 
areas that straddle vocabs. Topics are currently a good example; SIOC is 
stabilising and has its own sioc:topic, there is SKOS, and dc:subject 
... and discussions in SKOS scene about how to relate between a thing 
described as a topic (eg. the topic of Paris) and the "thing itself" 
(ie. the City). Geography is another one.

On the SemWeb, describing things in detail will very often involve 
combining namespaces. And there are no solid conventions for doing so. 
The Dublin Core community calls these combinations "application 
profiles" btw. I have some draft ideas floating around from those 
discussions I should dig out and post. One thought I keep coming back to 
is the use of a SPARQL query directory (even just a wiki) that keeps 
some common multi-namespace patterns in a form that allows them to be 
cited, linked, annotated etc. This appeals to me as a technique that 
might bridge from human-oriented use cases ("I want to find opening 
hours of shops that sell XYZ in Bristol, and their telephone number", "I 
want to find people interested in Iraq, who are qualified as a 
journalist, and have been there", "I want to find free software that can 
read this file format" ...) ... with machine-oriented formats. In 
practice I think a SPARQL directory would have *lots* of queries, rather 
than one per "application profile", since requirements vary slightly all 
the time, as do the contents of data-sets. My original thinking was that 
a single or handful of such queries could capture each "combination" of 
namespaces, but I now think that a little unrealistic.

What I'd like to do to explore this further, ... is migrate the FOAF 
wiki to use openID and (semantic)mediawiki, ... restrict edits to people 
logging in via openID, ... and make a SPARQL query directory prototype 
on top of that as a light-ish-weight platform. Plausible?


> Henry

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