Simplifying Clarification of Bidirectional Interface to help resolveSCA Assembly Issue 4

[Tom Rutt <tom@coastin.com>]

This email proposes a clarifying interpretation of the
definition of Bidirectional interface, which would simplify
the resolution of Issue Assembly-4
(http://www.osoa.org/jira/browse/ASSEMBLY-4 )

Section 8.2 of the Assembly WD02 defines Bidirectional
Interface. The second paragrapn (lines 2222-2224) currently
states”
“
An interface element for a particular interface type system
must allow the specification of an optional callback
interface. If a callback interface is specified SCA refers
to the interface as a whole as a bidirectional interface.
“

Lines 2231-2237 currently state the following;
“
If a service is defined using a bidirectional interface
element then its implementation implements the interface,
and its implementation uses the callback interface to
converse with the client that called the service interface.

If a reference is defined using a bidirectional interface
element, the client component implementation using the
reference calls the referenced service using the interface.
The client component implementation must implement the
callback interface.
“

This simple definition only implies that a Bidirectional
Interface has two separate interface types, with opposite
directionality for client and server.

Any infrastructure a service is bound to must support the
correlation of an operation invocation with the receipt of
the response for that operation, as defined within the a
single interface type (e.g., for WSDL Soap bindings this is
done thru the use of http request/response message pairs).

However, there is nothing in the definitions quoted above
that implies that the infrastructure must correlate the
invocation of an operation type on the callback interface
with an earlier invocation of another operation type on the
service interface of a bidirectional interface.  In fact,
the notion of callbackID (which appears in the Java
Annotations and API spec), does not appear in the Assembly
spec.

The notion of bidirectional interface / callback interface
can be greatly simplified if the assembly spec clarifies
that the infrastructure has no requirement for correlating
the invocation of an operation on a callback interface with
the invocation of an operation on the service interface. 
With this simplifying clarification, any required
correlation can be provided by the application specific
design of the service and callback interfaces (e.g, the
Purchase order number from the service interface operation
invocation message would appear as a parameter in the
callback interface operation invocation message for any
subsequent invoice).

All that is required for the infrastructure binding of a
bidirectional interface, is for it to be able to “wire” the
bidirectional interface’s service and callback interfaces
in a paired and complimentary manner.


Tom Rutt

-- 
----------------------------------------------------
Tom Rutt	email: tom@coastin.com; trutt@us.fujitsu.com
Tel: +1 732 801 5744          Fax: +1 732 774 5133