Re: [oslc-automation] Fw: Proposal: Link header in responses to AutomationRequest creation

[Tim Friessinger <TFRIESS@de.ibm.com>]

Hello,

when I read the Auto V2 spec some time ago, I thought the idea is, that an
OSLC Automation Service Provider can return an Auto Result as response to
the Automation Request POST action by a client.
With that returned Auto Result comes of course the URI of this Auto Result
(rdf:about), so the client knows how he can refresh/ update this Auto
Result without the need for doing a query.
I think this wasn't mentioned explicitly in the spec, but it was at least
how I thought it makes sense. ;-)

So basically it's the same idea as the Link option, proposed by Samuel, but
maybe a little bit more "OSLC style":
In Auto V3 one could specify that a POST action for an Automation Request
returns at least an Auto Result stub, so even if execution is delayed, the
client has at least the URI where to fetch the Auto Result again,
to see if meanwhile something happend.

Mit freundlichen Grüßen / Kind regards

Tim Friessinger

System Automation for z/OS Development
IBM Software Group, Tivoli
IBM Lab Boeblingen, Germany
                                                                       
                                                                       
                                                                       
                                                                       
                                                                       
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             Martin P Pain                                             
             <martinpain@uk.ib                                         
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             org>                                                      
                                                                   Subject
                                       [oslc-automation] Fw: Proposal: 
             12/02/2014 11:10          Link header in responses to     
             AM                        AutomationRequest creation      
                                                                       
                                                                       
                                                                       
                                                                       
                                                                       
                                                                       




Forcing OSLC Automation servers to implement a full query engine seems like
too high a barrier for entry, when the standard interaction only requires
the client to be able to find a result for a given request.

Please read & comment on the proposal below.

Thanks,
Martin

----- Forwarded by Martin P Pain/UK/IBM on 02/12/2014 10:09 -----

From:        Samuel Padgett <spadgett@us.ibm.com>
To:        oslc-automation-comment@lists.oasis-open.org
Date:        20/10/2014 18:23
Subject:        [oslc-automation-comment] Proposal: Link header in
responses to AutomationRequest creation
Sent by:        <oslc-automation-comment@lists.oasis-open.org>



Currently, as I understand it, Automation clients must query to find the
AutomationResult for an AutomationRequest they created. Something like

oslc.where=oslc_auto:producedByAutomationRequest=<request-uri>

This requires at least two requests, one POST for the AutomationRequest and
one GET to find the AutomationResult. It also forces servers to support
OSLC query. As someone who has written several OSLC providers, I can say
query is a lot of work to implement and difficult to get right.

I propose we add an optional Link response header [1] in responses to OSLC
AutomationRequest creation. This is an optimization to remove the query
step. For example,
HTTP/1.1 201 Created
Content-Length: 0
Link: <http://example.com/auto/result/82>; rel="
http://open-services.net/ns/auto#produces";; anchor="
http://example.com/auto/request/82";
Location: http://example.com/auto/request/82



Here a client can discover the AutomationResult just by looking at the Link
headers on the POST response.

We could relax the MUST requirement for queries if a provider supports the
Link header. Providers that don't immediately create an AutomationResult
for an AutomationRequest could leave off the Link header and continue to
use query.

Link is used in several places in LDP 1.0 [2], and we've used it in OSLC
3.0 resource preview drafts [3].

[1] http://www.ietf.org/rfc/rfc5988.txt
[2] http://www.w3.org/TR/ldp/
[3]
https://tools.oasis-open.org/version-control/browse/wsvn/oslc-core/specs/resource-preview.html?rev=42&sc=1#linkHeader

--
Samuel Padgett | IBM Rational | spadgett@us.ibm.com
Eclipse Lyo: Enabling tool integration with OSLC
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