Re: [sca-assembly] TIBCO eventing proposal

[Scott Vorthmann <scottv@tibco.com>]

Responses inline, Anish...

Scott


On Nov 25, 2009, at 11:45 PM, Anish Karmarkar wrote:

> Thanks for sending this out. Even though pictures/examples are missing, I *think* I get the general idea. Few questions/comments about the details (not the overall design) that immediately came to mind:
> 
> 1) Section 3.1 Exposing a Service as a Consumer says "The name of such an operation is understood to define an event type ..."
> Can you elaborate on why the operation name has to define the event type? Perhaps I misunderstood what the doc says, but from an event processing perspective, I don't think you want to restrict which events are delivered to a method based on its method name. For example, an onMessage(...) method may (and typically does) processes any event that is delivered. The name onMessage has no relevance wrt which event types it wants to consume.

This is a question of programming style.  The self-dispatch style of event handling you mention should not be ruled out, but as a developer I would prefer to write to a pre-dispatched interface, "printerOn(...), printerOff(...), etc.".  JAX-WS considers this style appropriate and developer-friendly, after all.

If the Java TC wishes to define annotations to support one-method, self-dispatching consumers, that's fine, but we don't believe it is necessary, given the existing mechanisms for one-way operations with JAX-WS.

> 
> 2) Section 3.2 Exposing a Reference as a Producer does not say anything about the cardinality of the reference. I assume it is 0..n.

Actually, I expect it is always 0..1 for one-ways.  There are no responses coming back, so no use-case that makes sense to me for 0..n.

> 
> 3) WRT the minimum-novelty goal, I should point out that the W3C WSRA WG that is standardizing WS-Eventing and friends has found the need to separate the event type description from WSDL. See http://www.w3.org/2002/ws/ra/edcopies/wseventing.html#Advertising  There is also a plan (not sure if it is approved by the WG yet) for refactoring the event description part in a separate spec in the WG. Trying to fit/overlay event description into the WSDL portType/method model does have its problems.

Perhaps.  We should discuss those problems.  Our main point is this: even if we deem it useful to define a specific metadata model for event types, we should fit it into our existing extension point for interface metadata, and define a mapping to/from WSDL.

> 
> 4) In Section 7 Domain Channels, is your objection to the syntax or to the fact that a pub/subcriber deep down in a nested composite is "connected" to a domain-level channel, i.e. visibility issue?

The latter, visibility.


> 
> 5) WRT channelBinding.sca, is that really necessary given that binding.sca is magic anyway? Wouldn't binding.sca fit the bill?

The issue here isn't the semantics, rather just the XML mechanics (or UML if you like).  From a modeling and schema perspective, "bindings" live on references and services.  We need something else to live on channel, consumer, producer.

> 
> Thanks!
> 
> -Anish
> --
> 
> On 11/25/2009 5:13 PM, Scott Vorthmann wrote:
>> Here is our proposal, in not a great deal of detail.  We'll have pictures and examples next week.  ;-)
>> Scott
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