[TAP] metadata

[Patrick Dowler]

The TAP spec currently specifies metadata (needed to write queries) in several 
ways:

TAP_SCHEMA is an information-schema-like approach where the service provides 
standard "tables" containing metadata about other tables.

VOSI-tables is a way to request an XML description of all the database content 
from the service. This same metadata (VODataService format) could be 
available (whole or partially) in a registry.

Tableset query: this returns a complete description like VOSI-tables (same 
format?) and in future might allow for conditions so that one got a portion 
of the metadata. I will admit that I do not understand the motivation for 
this.

The content of the metadata in TAP_SCHEMA and VODataService is supposed to be 
(must be?) the same or else one or both of them will be insufficient. They 
currently allow one to describe a schema(ta), table(s),  and column(s) but 
not functions (needed to use ADQL region) and does not describe keys and/or 
how to do joins between tables.


What is the minimum that we need for TAP to be useful? What is missing?


PS-please comment with respect to the recently posted TAP 0.41 (content 
unchanged since 0.3 but page/section numbering has changed)


-- 

Patrick Dowler
Tel/Tél: (250) 363-0044
Canadian Astronomy Data Centre
National Research Council Canada
5071 West Saanich Road
Victoria, BC V9E 2M7

Centre canadien de donnees astronomiques
Conseil national de recherches Canada
5071, chemin West Saanich
Victoria (C.-B.) V9E 2M7