SODA gripes (4): Mandatory multiplicities considered harmful

[Paul Harrison]

On 2016-02 -10, at 23:13, Patrick Dowler <pdowler.cadc at gmail.com<mailto:pdowler.cadc at gmail.com>> wrote:

And now the "see below": well, UWS doesn't provide much in the way of support for jobs that produce multiple results and partial success in doing so (aka no support at all). If input params are invalid I just make the whole job fail, but i have no way to report that:

- some combinations of ID and "bounds" do not intersect the target data
- I failed for some (transient) internal reason
- I can't provide some results because of authentication/authorization requirements

In sync you have suitable HTTP status codes for all of these.

I am not sure that it is fair to say that there is no support for these cases in UWS - there is an error message that can be convey the text of what is wrong - there is admittedly not an additional error code for classes of error, but the standard itself does mention the possibility of partial results being available in the case of job error, and given that results have to appear at a URL then it could be argued that you could convey exactly the same information at each result URL as you could in a synchronous case. In fact the asynchronous job pattern does allow signalling partial success of only some of the results being available where the synchronous one does not, because you could have some results signalled as OK and others with an appropriate HTTP error code.

In the end theses sorts of things come down to whether HTTP is regarded as part of the protocol or just a transport mechanism for the protocol. This has been a bit of a grey area in IVOA standards, - the Simple series actually only indicate errors via the internal status codes for instance. It is useful to piggyback on HTTP conventions though, and this is an argument for having UWS results always only appear at URLs rather than in-line in the the job description document.

Cheers
Paul..



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