[foaf-dev] location display. V1: current location

[Story Henry]

On 12 Jun 2008, at 17:11, Simon Reinhardt wrote:

> Story Henry wrote:
>>
>> 2.1.1 using foaf:based_near
>> ---------------------------
>> So first off we need an ontology to describe the current location  
>> of a person. At first I thought that the foaf:
>> :me foaf:based_near [ geo:lat 48.402495; geo:long 2.692646 ].
>> [snip]
>
> It works fine if you put the information into a separate file.
> [snip]
> { :me foaf:based_near [ geo:lat 48.402495 ; geo:long 2.692646 ]
> } dct:date "2008-06-12T12:00:00"^^xsd:dateTime .
> [snip]


Yes, that requires lifting rules and close attention to context. I  
wrote this out in more detail here some time ago:

http://blogs.sun.com/bblfish/entry/it_s_all_about_context

Now we always have to pay attention to context, but for our OWL  
reasoners to work well it would be best if we had ontologies that  
required as little as possible of it. If we can work in monotonic  
environments as much as possible, all the better. In ontologies I  
think we should try to help propagate good practices. In any case we  
will need the notion of time slices of 4 dimensional things all the  
time.

> Although I understand based_near more like a stable position, where  
> you live.

    <based_near>     a rdf:Property,
                 owl:ObjectProperty;
          :comment "A location that something is based near, for some  
broadly human notion of near.";
          :domain wgs:SpatialThing;
          :isDefinedBy <>;
          :label "based near";
          :range wgs:SpatialThing;
          vs:term_status "unstable" .


I understand based_near to be just a vague distance relation between 2  
spatial things. Now it makes most sense to speak of things that don't  
move a lot as being based near other things that don't move. Then one  
does not have complicated questions to answer regarding the context at  
which the statement was made. But I think it should be ok to think of  
a time slice of me as being based_near Paris, and another time slice  
of me as being based near new york. I think it would be possible to  
say that a foaf:Person who never left paris was based near Paris. But  
perhaps I am misinterpreting the intent of the relation. It is  
unstable, so perhaps some clarifications would be helpful.

Interestingly due to relativity theory one should be able to say that  
the a seat in a plane is based near the plane, right?

:seat22 foaf:based_near :747_n1231 .

or

:henrysHand foaf:based_near :henry .


> Talking of events, this seems like the perfect case for the Event  
> ontology [2]. An example:
>
> :me event:isAgentIn [ # Note that this inverse property is  
> deprecated but it makes it easier to write this in RDF/XML.

in N3 you can also write

:me is event:agent of [

>
> 	a event:Event ;
> 	event:time [
> 		a tl:Interval ;
> 		tl:at "2008-06-12T12:00:00"^^xsd:dateTime ;
> 		tl:duration "PT1H"^^xsd:duration
> 	] ;
> 	event:place [
> 		geo:lat 48.402495 ;
> 		geo:long 2.692646
> 	] ;
> 	event:factor :mytv , :mybeer ;
> 	dct:description "Havin' a Bud, watchin' a game"^^xsd:string
> ] .
>
> I really like this ontology and think it should deserve way more  
> attention. :-)

yes, events and objects are two really key pieces in logic. I remember  
an article where David Lewis tries to tease out the difference between  
them. If you think of it, it's not that easy, because both objects and  
events are defined by him as spacio temporal regions. I remember he  
ended up having a very neat way logical way of transforming one into  
the other. I don't have my books handy here.

So I think I could go with an event ontology to do what I needed.  
After all our time slices will never be far from an event we are doing  
during that time slice...

Anyone else any thoughts on this? ...


>
>
> Regards,
> Simon
>
> [1] http://blogs.sun.com/bblfish/entry/rdfauth_sketch_of_a_buzzword
>   rdfs:seeAlso <http://blogs.sun.com/bblfish/entry/foaf_ssl_creating_a_global 
> > .

yes. :-)

> [2] http://motools.sourceforge.net/event/event.html
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