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Re: InverseFunctional properties are the new URI?

From: Simon Price <simon.price@bristol.ac.uk>
Date: Thu, 29 Jul 2004 21:33:44 +0100
Message-ID: <41095F28.1030209@bristol.ac.uk>
To: Dan Brickley <danbri@w3.org>
Cc: Phil Dawes <pdawes@users.sf.net>, www-rdf-interest@w3.org

And, of course, IFP's may not be enough either in some circumstances. 
For example, where descriptions are partial and non-overlapping or where 
different (but both correct) IFPs are available in a pair of RDF 
descriptions, then smushing becomes non-trivial.

For hand-crafted RDF, it is likely that the author will provide nice 
IFPs but for generated RDF (e.g from web mining) there may well be no 
IFPs. So, really we have a sliding scale of convenience for smushing 
RDF: URI > IFP > no URI/IFP. Hence, Dan's point about unrealistic 
expectations about URIs in the early days could be extended to cover 
IFPs at the present. A whole class of interesting applications of the 
Semantic Web are likely to arise where smushing is required without 
either URIs or IFPs.



Dan Brickley wrote:

> * Phil Dawes <pdawes@users.sf.net> [2004-07-29 17:52+0000]
>>Hi All,
>>I've noticed that some RDF specs (including FOAF and DOAP) use
>>inverseFunctional properties instead of URIs to identify instance
>>I can see an instant benefit in doing this - end users don't need to
>>worry about the problems of minting URIs, maintaining them etc..
>>Is this the way RDF is going - URIs for the schema, BNodes with
>>InverseFunctional properties for the instancedata?
>>What are the consequences?
> I think we'll always need both. 
> In FOAF I've tried to be pragmatic. When "what is 'the' URI for a
> person" silliness was holding up deployment, FOAF encouraged an 
> emphasis on reference-by-description techniques. OWL subsequently gave
> us a way of expressing simple reference-by-description strategies in a 
> machine readable way. But FOAF doesn't rule out the possibility of their 
> being URIs for people, companies, etc. It just doesn't let the current 
> lack of such things get in the way.
> Rob McCool and Guha in their TAP work take a similar line, advocating 
> reference-by-description as a useful strategy for merging Web data.
> http://tap.stanford.edu/tap/rbd.html
> http://tap.stanford.edu/sw002.html
> I think in the early days of RDF there was something of a fairytale
> quality to the way URIs were perceived - basically a myth that all 
> interesting and description-worthy things will have well-known URIs.
> FOAF and reference-by-description in general shouldn't be taken as an
> attack on URIs as such, but as advocacy that other techniques are 
> useful too, and that we can write applications that figure out 
> common references without all parties necessarily sharing the same URIs 
> or even identifying expressions.
> All that said, we've a long way to go before all RDF toolkits support 
> InverseFunctional-based identity reasoning "out of the box"...
> Dan


Simon Price, Technical Consultant, Internet Development Group
Institute for Learning and Research Technology
Received on Thursday, 29 July 2004 16:33:48 UTC

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