DataLink RFC period annoucment

[Patrick Dowler]

I think the idea of describing service output in the DataLink service 
descriptor is interesting and it is something I thought about. The 
current use cases revolve around two things:

1. The {links} response solves a variety of discover->download issues 
such as (i) multiple files per dataset, (ii) alternate representations 
like previews, (iii) related resources (other sources of metadata, 
services that can act on the data).

2. The service descriptor was originally conceived to solve the problem 
of getting from a discovered ID (eg in a TAP or SIAv2 query response) to 
the {links} resource itself *without* having to resolve the ID via 
registry lookup....

We quickly realised that with minimal additional metadata we could use 
the same mechanism to go from the discovered values to any service that 
took them as input (the 3 service params and the inputParams)...

We also realised that the {links} response, since it is a votable, could 
also use service descriptors to describe services (typically lower level 
access services). Of course, one can put such links directly in the data 
discovery response *if* the cardinality of their discovered records and 
services matches (eg if one identifier in the discovery response can be 
used to call a service, then you can tell the client about it). That's 
the whole thing about links: you can add them anywhere you have an 
identifier that can be used someplace else! But that was not new spec, 
just new usage.

But, this is all aimed (currently) at forward-linking and how to 
describe the call to the service. We have not tried to describe what the 
service will actually do nor the response it might create. For now (1.0) 
I don't think we need it for the use cases at hand. Further, since we 
probably do want to add it later, I feel strongly that we should not add 
any simplictic form that we might regret. As has been mentioned 
elsewhere, PDL, VO_DML, and several other new-ish things cover some 
common ground and we should take the time to consider them and prototype.

I think that means adding desciption of the output in DataLink-1.1

my 2c,

Pat

On 21/07/14 03:10 AM, Jose Enrique Ruiz wrote:
> I think this could be solved just adopting the <GROUP
> name="outputParams"> mechanism

-- 

Patrick Dowler
Canadian Astronomy Data Centre
National Research Council Canada
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Victoria, BC V9E 2E7

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