capability and @version [was: Home for the UWS Registry Extension?]

[Markus Demleitner]

Hi Grid,

On Mon, Jun 25, 2018 at 02:13:34PM +0100, Mark Taylor wrote:
> On Mon, 25 Jun 2018, Markus Demleitner wrote:
> > As long as we have not identified strong use cases to discover by
> > minor version, my take would be: interfaces declare the highest
> > version they implement.  That would cover the "I need some extra
> > feature only available since version 1.2" use case, which currently
> > is the only discovery use case I find somewhat credible.
> 
> First, we're not just talking about discovery in the registry here,
> this also applies to enumerating interfaces in a service's capabilities 
> endpoint, and one can imagine 'discovery' use cases in that context
> that are a little bit more flexible.  I agree that it's hard to

Yes, true.  Again, we'll have to figure out the use cases and
requirements for, well, let's call it the VOSI case.

> advertise in the /capabilities document both a 1.1 and a 1.2
> version - e.g. because the implementation code has changed
> significantly between the two (they have different bugs) and
> they want to allow the (well-informed) user to choose between them.

Data providers out there: Have you found it necessary to do that?
Based on your previous experience: Do you anticipate that need?

> Second, I don't think this applies only to minor versions.
> If at some point in the coming decades we have a TAP 2.0
> then there will be reasonable discovery use cases that wish to
> distinguish between 1.* and 2.* versions.

Current practice with SIA (which I think is sane) is that a major
version gets a new standards record with an identifier of its own and
therefore is, as far as the registry goes, completely independent of
the previous major version.  They would therefore have a different
capability element -- which seems quite appropriate to me.

But I may be fooling myself -- perhaps we should ask on DAL and Apps
if people think the SIA major versioning technique works for them?


       -- Markus