TAP 1.0: sync vs async

[Gerard]

Dear colleagues

In the recent interop the issue of whether support for synchronous queries
should be mandated, or async, or both was mentioned, but not really
discussed further in the relevant sessions. I would like to once more bring
this up though.

My proposal is still that we mandate that sync OR async is supported, or
both.

There are use cases where sync allone suffices, and whatever some experts
argue, sync is easier to support in a robust manner than async.
On the other hand there are use cases where async is clearly the best
option, and sync might never be desired, so async alone should also be
possible.
We have had discussions on the mailing lists some months ago and I guess we
do not need to rehash those.

One "argument" against leaving it optional to support sync is that the VOSI
requests are currently implemented on the sync/ end point.
Irrespective of how we decide on sync vs async, I propose the VOSI requests
should NOT be put on top of the sync/ end point, but "next to" sync/ and
async/. They are different things from the actual service requests and
should/need not be mixed with them.

All these points were discussed with various people right after the closing
of the interop, when I realised that they had not been discussed.
There was general agreement (about 8 people were included in the discussion,
I will keep their identities secret) on all these points.
I promised to bring this up during the RFC, so here you have it.

Best regards

Gerard