Mapping of TAP_SCHEMA.columns.principal to SCS VERB

[Patrick Dowler]

I never payed much attention to principal in TAP nor in VERB (in
SIAv2) but iirc I only implemented 2 levels of verbosity in SIAv1 that
would then map to principal. I never saw how more levels of verbosity
would be useful... to me it is minimal/important vs everything.

Now when I implement SCS-1.1, I would probably have to make that kind
of decision because the source catalogues we host have hundreds of
columns and to do it Id have to get the curator(s) to assign values to
principal in the tap_schema... I'd probably suggest they pick ~20
columns with principal=true (1) and end up with effectively 2 levels
of verbosity in SCS. I'm pretty sure that's allowed as it was in
SIAv1.

my 2c,

Pat

On 10 October 2017 at 03:02, Marco Molinaro <molinaro at oats.inaf.it> wrote:
> Hi Markus,
>
> 2017-10-10 10:29 GMT+02:00 Markus Demleitner
> <msdemlei at ari.uni-heidelberg.de>:
>>
>> Hi,
>>
>> On Mon, Oct 09, 2017 at 03:32:40PM -0700, Walter Landry wrote:
>> > In the current TAP PR, TAP_SCHEMA.columns.principal is an integer.  Is
>> > the intention to make that map to the same meaning as SCS's VERB?  It
>> > seems that the meaning is somewhat inverted.  So
>> >
>> > SCS VERB    TAP principal
>> > 1           2
>> > 2           1
>> > 3           0
>>
>> Hm -- frankly, I think I'd like that.  I'm always fond of
>> streamlining things between the various protocols.
>>
>> The question is: Will this break any client?  And if it were, would
>> the breakage be serious?
>>
>> Client writers: Do you do anything with principal?
>
>
> In the TAP_SCHEMA manager that we have, we use it as a flag.
> Changing it to an enumeration of levels would mean changing
> the interface, even if I don't think it would be dramatic.
>
>> The very least we could do in 1.1 is prepare for this move and say
>> something like "clients should compare against zero and non-zero,
>> never against 1, as future versions of this standard may assign
>> additional semantics to different non-zero values".
>
>
> That would of course save my issue above, at least for now.
>
> But, apart from this apps-side, really I think that principal and VERB
> are two different concepts here and I'm not sure I'd like to pull them
> together, despite I don't know I much principal is used by
> service consumers, probably they rely more on indexed.
>
> Marco



-- 
Patrick Dowler
Canadian Astronomy Data Centre
Victoria, BC, Canada