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Subject: Re: [sca-bindings] ISSUE-48: How are mayProvide intents on bindingssatisfied


I agree with this proposal. Mike has gone a bit beyond what I had said 
when I proposed opening the issue and his specificity is an improvement.

Another thread that came out of the discussion on today's call was the 
following.
Vendors are free to add binding types to their implementations. We 
should add some words to the spec on what needs to be done when a new 
binding is added wrt mayProvides and alwaysProvides.

All the best, Ashok


Mike Edwards wrote:
>
> Eric,
>
> Let me try to give my perspective on this issue.
>
> The core of this issue is that:
>
> IF a bindings specification says that a given binding has a non-null 
> @mayProvide attribute
>
> THEN that bindings specification MUST define how the intents 
> identified in the @mayProvide attribute
> are provided by that binding.
>
> - and the binding.jms binding seems to fall into this category (I 
> think you agree on that)
> - but that specification does not say anything about how those intents 
> are provided
>
>
> OK, to open the discussion a bit more. I would expect that if some 
> binding said @mayProvide="xx yy",
> where "xx" and "yy" are some intents, then some configuration of the 
> binding is required in order to
> have those intents satisfied - if no configuration was required, then 
> I'd expect those intents to be in
> the @alwaysProvides list....
>
>
> Typically, I'd expect such configuration to be part of the parameters 
> defined by the binding spec.
> eg. Intent "xx" is provided by this binding if parameter "foo" is 
> given the value "bar"
>
>
> The whole question of whether a binding should declare @mayProvide 
> intents at all is a different
> question. There seem to be two potential approaches to this. One is to 
> say that the provision of
> specific intents is (surprise surprise) a question of Policy - and 
> should be handled through the use
> of concrete policySets that can be applied to the binding. The other 
> is to use binding parameters,
> as defined by the specification. There are no hard and fast rules here 
> - either is acceptable.
>
> I argue that where a well defined body of Policy exist already, it 
> would be wise to use it. So in the case
> of binding.ws, there is the WS-Policy specification and policies that 
> relate to it. However, for other kinds
> of binding, policy of this type is not well established in the 
> marketplace and so it may be preferable to
> use configuration parameters - this may well be the case with JMS, for 
> example.
>
>
> So - how to resolve this issue?
> At the very least the binding.jms spec needs fixing - possible 
> resolutions:
>
> 1) remove the statements about @mayProvide
> 2) define how the intents mentioned in @mayProvide are actually 
> provided - ie what configuration is
> needed in order for the user to get those intents when using the binding.
>
> I think it is also worth the TC thinking about the other binding specs 
> - as to whether they should have any
> @mayProvides intents. The answer may be "no" - but it should be a 
> considered "no".
>
>
> Hope this helps....
>
>
> Yours, Mike.
>
> Strategist - Emerging Technologies, SCA & SDO.
> Co Chair OASIS SCA Assembly TC.
> IBM Hursley Park, Mail Point 146, Winchester, SO21 2JN, Great Britain.
> Phone & FAX: +44-1962-818014 Mobile: +44-7802-467431
> Email: mike_edwards@uk.ibm.com
>
>
> From: 	Eric Johnson <eric@tibco.com>
> To: 	OASIS Bindings <sca-bindings@lists.oasis-open.org>
> Date: 	08/10/2008 18:41
> Subject: 	Re: [sca-bindings] ISSUE-48: How are mayProvide intents on 
> bindings satisfied
>
>
> ------------------------------------------------------------------------
>
>
>
> OK, now that I've logged the issue, I'm going to argue for why we
> shouldn't open it.
>
> Eric Johnson wrote:
> > Logged as: http://www.osoa.org/jira/browse/BINDINGS-48
> >
> > -Eric.
> >
> > ashok malhotra wrote:
> >
> >> The SCA Policy spec says that in addition to the intents that a
> >> bindingType alwaysProvides
> >>
> Point #1.1 - The first item in the description flags that other work
> might be appropriate for other TCs first.
> >> "... The binding type also declares the intents that it may provide by
> >> using the optional @mayProvide attribute. Intents listed as the value
> >> of this attribute can be provided by a binding instance configured
> >> from this binding type."
> >>
> Point #1.2 - Still seems to be relevant only to the policy specification.
> >>
> >> My assumption was that, to use some of the mayProvide intents, a
> >> binding instance had to be configured outside of SCA and then that
> >> instance used for some service/reference. At last week's Policy f2f,
> >> it became clear that this assumption was not universally shared. Some
> >> thought that the SCA runtime would configure the binding instance
> >> during the deployment phase.
> >>
> Point #2.1 - Looking through the existing specifications, the notion of
> a binding "instance" is discussed only in passing for the binding.ws
> spec, and not at all in binding.jms or binding.jca. The concerns raised
> in the above paragraph don't seem to have much bearing on the binding
> specifications that I see.
>
> >>
> >> I looked at the binding.ws, the binding.jca and the binding.jms specs
> >> and found that, as expected, binding.ws says nothing about mayProvide.
> >> Binding.jca does not say anything about mayProvides either.
> >> Binding.jms says
> >>
> >>
> >> <bindingType type=”binding.jms”
> >> alwaysProvides=”jms” mayProvide=”atLeastOnce atMostOnce ordered
> >> conversational”/>
> >>
> Aha! Finally, something specific to one of the binding specifications.
> Perhaps a glimmer of an issue? Except:
>
> Point #3 - As stated the above doesn't actually raise an issue. JMS
> spec is clearly different from the other two, but is this one right, and
> the others wrong? I'm lacking in specifics to understand. Further, as
> issues editor, in I need to know whether this should be raised as one,
> two, or three issues, and I still cannot tell.
> >>
> >> but it does not say how the mayProvides intents are satisfied. That
> >> is, it does not say what configuration parameters can used to provide
> >> these intents.
> >>
> >>
> >> Thus, two requests
> >>
> >>
> >> - Clarify whether the binding instances configured to provide the
> >> capabilities indicated in mayProvides are generated separately,
> >> earlier and outside of SCA and then used in the SCDL or whether they
> >> are generated by the SCA runtime.
> >>
> Point #2.2 - Again, the notion of binding "instances" seems to lie
> outside of the binding specifications. Bindings specifications at this
> point do not talk about "generating" anything for runtime, except the
> binding.ws spec, which talks about WSDL.
> >>
> >> - As far as possible, indicate in the bindings specs which
> >> configuration parameters need to be tweaked and how to satisfy the
> >> mayProvide intents.
> >>
> Point #4 - the term "configuration parameters" leaves me completely
> muddled - Is this something specified via policy? Does it appear in the
> composite file? Is it data that is part of the binding elements?
> Further the notion of "tweaking" those "configuration parameters" sounds
> interesting, but leaves me completely in the dark as to what you think
> might be appropriate.
>
> This issue certainly has piqued my curiosity, and I suspect there is a
> very important issue to raise here related to one or more of the binding
> specifications, but I still flailing in a fog as to what that specific
> consideration might be. I would much prefer to see a new issue filed
> that identifies precisely which text in which specification(s) is
> problematic, why it is problematic with respect to issues already
> resolved in other TCs or the text of the other specifications, and
> hopefully even a suggested resolution.
>
> I'm also certainly happy with the notion that this is a topic of
> discussion as an agenda item, but that simply isn't the same as an issue
> to be raised.
>
> -Eric.
>
>
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