UCDs, metadata and AstroOntology

[Tony Linde]

> -----Original Message-----
> From: owner-semantics at us-vo.org 
> [mailto:owner-semantics at us-vo.org] On Behalf Of Anita Richards
> Sent: 16 October 2002 14:38
...
> In practice, catalogues might contain any information 
> anywhere...

I guess this relates to 'annotation' - the process of adding metadata to
articles, data tables etc. A big job but one that CDS does now and which
the bioinformaticians have obviously developed various bits of software
to help with.

> ... As I understand it, the UCDs _are_ the meta data 
> for each column but they are dynamic, ie built up out of 
> atoms from the column or the header or possibly higher levels 
> depending on the query.

I'm not sure I understand what you mean by them being dynamic. Once a
UCD is assigned to a column, it is fixed, n'est-ce pas?

> -----Original Message-----
> From: Guy Rixon [mailto:gtr at ast.cam.ac.uk] 
> Sent: 16 October 2002 15:48
...
> ... For me, UCDs ARE 
> metadata but ARE NOT names.

I think I'm getting the message now :)

And I guess I should have realised that from the name: unified column
DESCRIPTORS.

> I propose that a programme reading, say, a VOTable should be 
> able to find and use columns of that table for which it knows 
> the semantics independently of some ontological service.  

Which is basically saying that all or some of the metadata should be
embedded in the VOTable, so any piece of data should carry its metadata
around with it. I have no argument with that, though I guess in some
cases it'll be better not to (cannot think of an example offhand).

> 1. To make the parsing self-contained.  Collating bits of 
> metadata from many parts of a document makes a programme complicated.

I don't think I agree with that. To me, parsing is always more difficult
than looking in a specific place for a specific piece of data. If
metadata is carried in a specific place in the VOTable, it'll be
relatively easy for a program to look for it there and use it.

As you said above, UCDs are metadata, not column names, so why not use
the column names as the column names and store the metadata separately
in a form that makes it easy to access and use.

> -----Original Message-----
> From: Ray Plante [mailto:rplante at poplar.ncsa.uiuc.edu] 
> Sent: 16 October 2002 16:05
...
> Last week, a number of us attended a workshop at SAO on 
> developing data models for the VO...

Do you have a write-up on any papers presented or outcomes of the
meeting?

> As many of you know, I'm partial to a data-model-based metadata 
> definition;

I'm not sure what you mean by 'data-model-based metadata', Ray? Can you
explain this more or point to any papers you've written that expalin it?
Thanks.

Cheers,
Tony. 
__
Tony Linde                       Phone:  +44 (0)116 223 1292
AstroGrid Project Manager        Fax:    +44 (0)116 252 3311
Dept of Physics & Astronomy      Mobile: +44 (0)7753 603356
University of Leicester          Email:  ael at star.le.ac.uk
Leicester, UK   LE1 7RH          Web:    http://www.astrogrid.org