Mapping of TAP_SCHEMA.columns.principal to SCS VERB

[Marco Molinaro]

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
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