TAP documentation issues: VOSI

[Tom McGlynn]

1. Am I right that there are three ways to get metadata from a
TAP services:

-- Direct query of TAP_SCHEMA starting with the required tables.
-- Use of VOSI
-- Querying database with known, non-TAP_SCHEMA tables but setting
the maximum number of rows to 0 a la the Cone search.

2. The TAP document does not provide enough information to write support
fr the VOSI queries.  The VOSI document is also inadequate.  It looks
like the one needs to refer two levels down to the VODataService 
document to actually get sufficient detail to begin writing code to 
support the VOSI metadata query.  This document is extremely dense and 
gives no examples for tabular data.  Since this functionality is 
duplicating something that the user already has using the other metadata 
methods, we need to make it easy on implementors or they'll just forget 
about it. [That was my first inclination!]

If I understand this properly then there is a very close relationship
between the metadata tables parameters in TAP_SCHEMA and the XML 
requiredfor the VOSI table metadata query.  The TAP document should 
describe how the VOSI metadata query might be satified from the schema data.

3. Are the VOSI and TAP_SCHEMA metadata queries required to organize
tables in the same way?  E.g., I could imagine describing all tables 
inside a single '<TableSchema> element where the table names were
given as schema.table.

4. Does the TAP_SCHEMA and its tables need to be described in the 
metadata VOSI response?

5. I'm lost as to what I need to do to support VOSI getCapabilities.  As 
far as I can tell there's nothing that describes what the capabilities 
record for a TAP service should look like.  Does it just reuse the 
existing Catalog Service?  The only place I could find a reference to 
TAP was in discussing the table metadata.  I didn't see anything in the 
TAP document that indicates what the format of the capabilities record 
is to be.

I don't see any way around this problem, so we will not be implementing
VOSI getCapabilities until we can get some further clarification.


Doing getAvailability and getTableMetadata seems possible though TAP 
document itself provides little support for them.  Even if we want to 
leave the normative elements to other documents, putting examples in the 
TAP document would -- imho -- make it much easier for the TAP implementor.

6. Validators for the the syntax of the VOSI responses would be nice...