Definitions, costs and use-cases

[Rob Seaman]

Just a few quick comments - we'll have plenty of time to talk at the  
meeting.

On Sep 22, 2007, at 3:12 AM, Norman Gray wrote:

> I think various people _have_ discussed these before, possibly  
> implicitly, but certainly at length,

Very definitely, this has been discussed implicitly at length :-)

> so we can move toward more specific questions, which is where I  
> think Andrea has been trying to herd us.

Yes - specific use cases.  Even Ed admits:  "It will be damn hard to  
get the metadata into shape for this to work."  What would this hard  
work buy us, *specifically*?

> We won't get much from 200-year old dictionary definitions, or  
> technical abstracts from completely different domains  
> (philosophical ethics, as I recall), so here's the standard  
> definition from computer science (all together, class!):
>
>     an ontology is a formal specification of a shared  
> conceptualisation
>
> That is:
>
>     conceptualisation = a set of things/concepts/types, as appropriate
>     shared = ...which at least one other person agrees with
>     specification = ... and which you've written down
>     formal = ...in a machine-readable way

There were two points to bringing Dr. Johnson into the discussion.   
First, that even when discussing ontology itself, one starts with a  
definition.  Thanks for the improved definition, BTW.  This  
conversation seems to be casting ontology in opposition to  
vocabulary.  That itself seems counterproductive.  Second, the VO has  
to peddle its wares on the astronomical open market.  An astronomer  
will understand keywords and vocabularies.  From what I've seen, they  
won't understand what ontology means.  So either this has to be  
hidden behind something like a vocabulary list - or a domain-specific  
case has to be built for astronomy.

> Costs
>
> [...] handling an ontology requires one of several types of reasoner 
> [1].
> [1] A 'reasoner' is something which, for example, deduce that an  
> instance of a given subtype is also an instance of the type.

So the basic issue is whether the value of such reasoning toward  
performing a specific astronomical task is worth the overhead (in  
various parameters) of a reasoner (and of generating the ontology the  
reasoner is reasoning against).

> Note that not every application necessarily benefits from more  
> expressive structure.

I see we agree.

> Myself, I think that SKOS (taxonomy/thesaurus) provides most of  
> what you really need, and can reasonably acquire, to support  
> searching.  Ed is a more unequivocal enthusiast for OWL.

I see you and Ed disagree.

> The upside, from the point of view of acquisition costs, is that  
> most of the sciences, with their journal keywords, and the  
> systematising mindset of their users, can probably get on to the  
> second rung for free.  The much-lamented lack of interest in the  
> IAU keyword list suggests that getting on to the third rung might  
> be a struggle.

Well, more to the point, this is evidence - predating the VO - that  
such functionality may be a mismatch to the astronomical community.

> Use-cases
>
> Mathilda is reading a paper online.

Thanks for this user scenario - it is a bit complex to be called a  
use case.  And thanks greatly for the insightful discussion.  We're  
assembling in the lobby for a walkabout, so I'll have to ring off  
now.  Perhaps we can continue this at the reception.

Rob