[oslc-cm] Updated State Predicates Proposal

[Steve K Speicher]

Paul McMahan/Raleigh/IBM wrote on 06/20/2012 01:21:08 PM:

> From: Paul McMahan/Raleigh/IBM
> To: Steve K Speicher/Raleigh/IBM at IBMUS, 
> Cc: oslc-cm at open-services.net, oslc-cm-bounces at open-services.net
> Date: 06/20/2012 01:31 PM
> Subject: Re: [oslc-cm] Updated State Predicates Proposal
> 
> > If a service provider supports state predicates on change requests,
> > then the state predicates MUST be queryable
> 
> It would be helpful clarify how that a consumer can detect that state 
> predicates are supported.  At one point we talked about checking the 
> resource shape for the query capability to see if the state predicates 
are 
> present.  But providing this resource shape is not a MUST requirement, 
so it
> might not be present.
> 
> The consumer needs to know if state predicates are supported because 
> otherwise the query results could be unpredictable.   For example, if a 
> consumer sent a query like oslc.where="oslc_cm:closed=true" then one 
service
> provider might include ALL of the change requests in the result but 
another 
> service provider might include NONE, depending on their interpretation 
of the spec.

I think a client in this case should issue oslc.select="oslc_cm:closed" as 
well.  It can then test for the existence of triples with this predicate 
in the query result, therefore the client will know (if it shapes are not 
supported) that the provider doesn't support it.

Not sure what else can be done in the 2.0 spec at this point.  It would 
make sense an integration with you have works "better" if shapes are 
supported, therefore you'd encourage those who want to leverage this 
integration end point to do this.  The fall back would be to have to run a 
query, inspect the results, to determine if the provider supports it.  You 
can always put additional requirements on some "key" integrations, ie 
require them to do query shapes and state predicates.

Perhaps a good scenario to contribute to the CM 3.0 backlog, sorry if 
there already and just missed it.

Thanks,
Steve Speicher | IBM Rational Software | (919) 254-0645