Re: Followup / proposed action

Hi Doug,

> If we describe the list of tables which a given service can access, the
> response is a table wherein each row describes one such Table object.
> The columns or fields of the table are the attributes used to describe
> a Table object. These attributes can be anything we want, regardless
> of how the information is conveyed or stored (this has nothing to do
> with VOTable, which is just a container).
>
> If we describe the list of columns or fields in a Table object, the
> response is a table wherein each row describes one such TableColumn
> object. The columns of the returned table are the attributes used to
> describe a data table TableColumn. Again, these can be anything we
> want (probably some combination of SQL92 and VOTable PARAM/FIELD-like
> attributes, but it is arbitrary).

I think we are talking at different levels here; if the metadata is embedded in VOTable as you describe, then existing tooling automatically understands how to *syntactically parse* that document, but not necessarily how to *semantically parse* it. We would have to define a competing standard expressing the *meaning* of the data encoded in those rows (as you say, "these can be anything we want"). The point about the VOResource description is that it already specifies both how to encode the metadata *and* how to interpret it.

I understand that it simplifies your own client coding to avoid the ingestion of VOResource (although XML libraries make ingestion of VOResource descriptions into an object model pretty trivial). If we were to mandate that TAP services provide their metadata in both VOResource and (e.g.) VOTable representations, then your services would only have to *export* the VOResource descriptions and your clients would not need to ingest them. Producing such descriptions is generally just a matter of populating a template, so not a vastly complex programming task.

Cheers,
Kona.

-- 
Kona Andrews        kea-at-roe.ac.uk
AstroGrid Project   http://www.astrogrid.org
IfA, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ