A suggested revision for UCDs

[Patrick Dowler]

On Wednesday 22 October 2003 10:43, Norman Gray wrote:
> I'm sure it is this which causes some people (I'm thinking of Gerard
> Lemson and Pat Dowler) to gasp and, in their poster, pick out pos_eq_ra
> for special deprecation as incoherent.  If you believe that principled
> generation of UCD words would be a Good Thing (and that would probably
> be my prejudice), then I suspect that paths in (say) Gerard and Pat's
> model would be a good way to do it (do Gerard and Pat claim that every
> UCD word is thus expressible?). 

That particular example was chosen to show that the different parts of
the POS_EQ_RA_MAIN (UCD1) are quite different types of things with
different realtionships to the thing being described. In the data model,
POS is the "position" phenomenon, EQ is a particular ReferenceSystem,
RA is one component of a point (the type used to represent a position
in that ReferenceSystem). I still don't know that MAIN would belong in a
data model. It isn't "incoherent" so much as it includes some very different
kinds of things.

In the concept;property style of UCD2, I don't think it is inconsistent with
the data model we presented. The difference between UCD and DM is
that in a model one  explicitly states the relationship between the 
concept and the property, So, for example, in our DM we are
expliclty saying that the relationship between a position and the 
ReferenceSystem is a different relationship that between the position and the 
RA (a component of the data type/structure). UCD2 leaves the relationship 
implicit by having only one relationship: "propertyOf". Whether that's good 
or bad thing is an open issue.


-- 
Patrick Dowler
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