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Re: Exactly what does broader/narrower mean?

From: Richard Cyganiak <richard@cyganiak.de>
Date: Mon, 19 Feb 2007 21:09:54 +0100
Message-Id: <EFC2E6DE-E022-4776-A887-47369CFA28D1@cyganiak.de>
Cc: public-esw-thes@w3.org, Sören Auer <auer@informatik.uni-leipzig.de>
To: Jakob Voss <jakob.voss@gbv.de>

Jakob, Mark,

Thanks a lot for the helpful answers. That clears it up.

Richard


On 19 Feb 2007, at 16:48, Jakob Voss wrote:

> Hi Richard, hi Sören,
>
> Looks like the group of people dealing with this aspects of knowledge
> organization is small so there are always the same people ;-)
>
> You wrote:
>
>> In Wikipedia, there are often category hierarchies like this:
>>
>>     Germany
>>       |
>>       +-- German politicians
>>
>> Can this be translated to SKOS?
>>
>> If Germany and German politicians are skos:Concepts, then is there a
>> skos:broader relationship between them?
>
> Yes - the hierarchical relations between Wikipedia categories are an
> application of SKOS.
>
>> I'm a bit concerned that one isn't really a sub-topic of the other.
>>
>> To phrase the question differently: Is there a clear test to  
>> decide if A
>> skos:broader B? For RDFS class hierarchies it's simple: A
>> rdfs:subClassOf B iff all instances of A are also instances of B.  
>> What
>> would be the equivalent rule for SKOS?
>
> We don't have instances in SKOS but resources that are indexed with
> concepts. The rule in SKOS may be:
>
> A skos:narrower B if all resources that are indexed with A may also be
> indexed with B.
>
> The point is that "may also be indexed" is a much more vague  
> constraint
> than beeing an instance also - and it depends on the context of your
> application. You may index all German politicians with "Germany" so
> users will find them when searching for "Germany". But if there are  
> too
> many resources indexed with "Germany" than it's better to select a  
> more
> detailed concept - it just depends on! Alistair presented the semantic
> model of cost expansion to deal with hierarchic relations in skos when
> doing retrieval, but this is only one possible application.
>
> Do you know Sorites paradox? Consider a heap of sand from which grains
> are individually removed. If you remove a single grain of sand of  
> it, it
> still remains a heap - so you may conclude that a heap may be composed
> by just one grain of sand! This is also the nature of skos:broader:  
> its
> a vague property. This may scare traditional AI fundamentalists,  
> but it
> allows practical usage with real world resources and people with real
> world information needs.
>
> Greetings,
> Jakob
>
>
> For limited Cost Expansions see: Alistair Miles: Retrieval and the
> Semantic Web, page 32ff
> http://isegserv.itd.rl.ac.uk/retrieval/
>
> For more about Wikipedia category hierarchies see
> Voss: Collaborative thesaurus tagging the Wikipedia way.
> http://arxiv.org/abs/cs/0604036
>
> The chapter about hierarchical relations in a student paper I wrote in
> 2003 may also be of interest. Today I would not write it in the  
> same way
> but the basics still apply:
> http://eprints.rclis.org/archive/00007589/, page 28.
>
>
Received on Monday, 19 February 2007 20:10:30 GMT

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