Ontology-based queries

[Tony Linde]

OWL sounds good - when are we likely to see the first editors/reasoners?

>
http://www.cs.man.ac.uk/~panz/Zhilin/download/Paper/Pan-Horrocks-datatyp
e-2002.pdf

Strewth! And I thought astronomy papers were difficult to read :)

Cheers,
Tony. 

> -----Original Message-----
> From: Sean Bechhofer [mailto:seanb at cs.man.ac.uk] 
> Sent: 16 October 2002 17:17
> To: Ashish Mahabal
> Cc: Tony Linde; semantics at us-vo.org
> Subject: Re: Ontology-based queries
> 
> 
> On Tue, 15 Oct 2002, Ashish Mahabal wrote:
> 
> >
> > Tony wrote:
> >
> > >On the other hand, if we modify the above query to be:
> >
> > > Object is-of-type SNR
> > >  AND Source registers-in-wavelength X-Ray
> > >  AND Object is-within (1 arcmin) of-region (05 25 00 -69 38)
> >
> > >I think we hit difficulties. I cannot see how an 
> ontology-based query 
> > >like this could work.
> 
> OWL will include support for (unary) datatypes, so this kind 
> of expression/query can be represented.
> 
> > The above query is likely to be expanded out to:
> >
> >  Object is-of-type SNR
> >   AND Source registers-in-wavelength X-Ray
> >   AND Object has-RA > x.y
> >   AND Object has-RA < z.w
> >   AND Object has-DEC > a.b
> >   AND Object has-DEC < c.d
> >
> > But then, as you imply, the question of a subclass versus 
> individual 
> > objects would arise and the query may have to be split into two 
> > sections: apples and oranges. Do just the first part first using an 
> > ontology:
> 
> There's no reason why an OWL query engine would not be able 
> to answer queries like this. As Ashish points out, the query 
> is likely to be answered through a division of labour between 
> the ontological part and the datatype part. OWL makes a clear 
> separation between datatype and object properties, and there 
> are proposed architectures for reasoners (see [1]) that will 
> support precisely this kind of query.
> 
> >  Object is-of-type SNR
> >   AND Source registers-in-wavelength X-Ray
> >
> > and then on the resulting set do the SQL like query
> >
> > select * where Object has-RA > x.y
> >   AND Object has-RA < z.w
> >   AND Object has-DEC > a.b
> >   AND Object has-DEC < c.d
> >
> > However, if we can store the classes (SNR, X-ray) with an 
> object along 
> > with its attributes (RA, Dec), we could do the two in one 
> fell swoop.
> >
> > Whatever way is chosen, an important point to remember will be that 
> > the query should magically rearrange itself so that the 
> first clause 
> > is likely to return the smallest number. Otherwise if we go 
> through a 
> > large number of objects only to throw away most of them at a later 
> > point, its a waste of resources. But perhaps this point 
> will come up 
> > much later.
> 
> Of course, query optimisation is essential. I would hope that 
> this would be part of the reasoner's responsibility, so a 
> client application would not have to worry about this (much 
> as is the case with standard query engines).
> 
> 	Sean
> 
> [1] 
> http://www.cs.man.ac.uk/~panz/Zhilin/download/Paper/Pan-Horroc
ks-datatype-2002.pdf
-- 
Sean Bechhofer
seanb at cs.man.ac.uk
http://www.cs.man.ac.uk/~seanb