getCapabilities

The topic of getCapabilties has come up and I for one am rather unclear about what is included in it. My reading of other specs and emails in DAL suggest that it is about whether or not a service supports optional ** methods **. I also recall it is the place to declare what version(s) of a protocol is/are supported.

So it may be applicable for describing whether a TAP service supports sync and/or async query methods (for example) but it does not look to me like it would be the place to describe the content model of the service (eg. database, table, and column metadata in TAP) nor does it look like the place to describe support for non-mandatory parts of the ADQL language (for example, UDFs). I am not sure about the latter, but to me ADQL is "input content" and not "service API".

Does typical DAL getCapabilities() include a method to get the registration (the VOResource)? Maybe that's the thing I missed that is the source of contention between it and TAP metadata...

I recall that it also includes a declaration of protocol versions. In SSA, does that include the version of the spectral model? If so, then a TAP capability may well include declaring the presence of and version of a data model describing the content (which IMO should imply that the service supports querying by utype, since that's the whole point of saying which model describes the content.. a la Source Catalogue Data Model effort).

Pat

PS-oops, scrollbar appearing on the left :)

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Patrick Dowler
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