A Working document has been submitted

[Doug Tody]

We had a similar discussion in the context of DAL a while back, and ended
up proposing a new tag UTYPE for this purpose.  UTYPE is a pointer into
a data model, and serves to identify the unique data model attribute
associated with, e.g, a field or column of a VOTable (and also thereby
indirectly associating all the attributes of a given data model).
The same field could also have a UCD, which serves a different purpose.

The idea goes like this:

    o	We formally define a data model somewhere on the Web within the VO.
    	This includes a namespace for each data model (and other things
	such as a schema, whitepaper defining the data model, etc.).

    o	A VOTable which uses a given data model (DM) will reference the DM
	namespace.

    o	Each UTYPE tag specifies the data model namespace, and the data
    	model attribute associated with the field or other data item,
	e.g., UTYPE=<dm><attribute>.

    o	The attributes of a data model can thus be mapped into votable
    	columns (or other structures), with the ability to rigorously
	identify and associate each such DM attribute.  One can then do
	things like extract the DM attributes and pass them off to 
	analysis software, go back to the published DM schema to autoverify
	the DM attributes, and so forth.

Both UCD (fuzzy knowledge tags) and UTYPE (rigorous pointer into data
model) have their place.  UCD provides a simple way to do semantic
associations without requiring data models, topic maps, etc., and UTYPE
allows one to reliably use data models, e.g., for data analysis or for
more precise queries.

	- Doug


On Tue, 7 Oct 2003, Wil O'Mullane wrote:

> I would rather hope we map not to UCD but to Data Model terms.
> We were rather thinking of this mapping being at perhaps a higherlevel
> so skynode would just respond to its own schema but some other portal 
> would take a query interms of UCDS and rewrite it using appropriate colum
> names. Another portal might do the same for Data Model terms etc..
> So Althoutgh I thinkthe SkyNode must publish its ucds I think any query
> comming in should be in terms of the proper column names..
> 
> > 
> > > I think it is essential that ADQL support theuse of *both* UCDs and column
> > > names. It'll be up to the query interface to substitute column names (by
> > > asking the user probably) where UCDs are not uniquely resolvable.
> > > 
> > > Cheers,
> > > Tony. 
> > > 
> > > 
> > >>-----Original Message-----
> > >>From: owner-voql at eso.org [mailto:owner-voql at eso.org] On 
> > >>Behalf Of Roy Williams
> > >>Sent: 07 October 2003 15:50
> > >>To: Clive Page; voql
> > >>Subject: Re: A Working document has been submitted
> > >>
> > >>
> > >>
> > >>>  Region ('CIRCLE J2000 19.5 -36.7 0.02')
> > >>
> > >>I have a question in the same style. I would like to start 
> > >>using the UCD ontology within VOQL. I am imagining metadata 
> > >>queries like
> > >>
> > >>select table where UCDMatch(table, "phys.velocity, src.galaxy") > 0.8
> > >>
> > >>in order to find tables that have galactic velocities. Can 
> > >>VOQL be extended in this way?
> > >>
> > >>Roy
> > >>
> > > 
> > > 
> > 
> 
>