content, format, ctype, or xtype ?

[Doug Tody]

Hi -

Despite having just written a long email on UTYPEs, I suggest we are
getting side-tracked.  TAP and VOTable should support pass-through
of UTYPE (and UCD), as these are important to be able to use TAP to
access data which has an associated formal data model - SimDB, the
generic dataset, etc.  But this is largely not a TAP issue so long
as the mechanism supports pass-through of the information.  We might
eventually want to be able to use UTYPE and UCD tags in queries but
that can come later.  We could get futher into UTYPE use cases but
I suggest it suffices for now to state that we want TAP to support
access to data containing UTYPEs.

The immediate issue Francois raised is simpler.  1) Do we want to
say something simple about the "format" of a single field/param
of a votable, and 2) if so what do we call the attribute used for
this purpose.

1) is still not clear although it appears that most feel this could
be a useful feature to add.

For 2), use of UTYPE is still not ruled out (as detailed in my other
message), however if we really want this feature, an independent
mechanism may be preferred, to avoid cases where UTYPE is already
used by a larger data model.

 	- Doug



On Mon, 4 May 2009, Rob Seaman wrote:

> Roy Williams wrote:
>
>> Can't we bring TAP back to its original limited purpose as an interface to 
>> a database?
>
> The nature of an interface is to tie two things together.  In this case, Roy 
> reminds us that on one side lie tables in a DB.  On the other side are VO 
> users.  Presumably there is a list of table-access use cases that TAP is 
> intended to address?
>
> How will users benefit from having TAP?  What specifically will applications 
> do with all these meta-metadata tags?  Assume the DM and representational 
> hooks are indeed carried in some fashion from point A to point B.  To what 
> purpose will they be put?  Or rather, will most of the knowledge of the 
> underlying tables be built into the purpose-built applications anyway?
>
> For instance, a typical VOish answer might be that a meta^2data rich TAP will 
> permit joins between foreign tables created (very, very carefully created) by 
> different institutions for different purposes.  Do we have specific such 
> examples in mind?  How do such use cases flow down to the details of 
> specifying [c|x|u]types?
>
> Rob
>