ISSUE 79: Proposed response

[Bryan Aupperle <aupperle@us.ibm.com>]

I propose that we respond to this comment
with the following  (this would part of a e-mail that is a response
to all of his comments): 

The C++ client and implementation specification
describes how SCA components can be implemented in C++.  This includes
definitions of <implementation.cpp/> and <interface.cpp/> as
well as the classes available to C++ component implementations. As described
in the Assembly specification, components can only be included in an SCA
domain when included in a composite.  The SCA runtime is aware of
the composite instance that a component implementation instance is contained
by.  However, there is no direct implementation of a composite.  A
composite instance is a collection of its component implementation instances
and as such has no direct representation in C++ (i.e. there is no class
corresponding to a composite) and Assembly concepts like promotion and
property value assignment are handled by the SCA runtime.

But because the SCA runtime is aware
of the composite instance that a component implementation instance is contained
by, it is possible have composite-scoped component instances.  Unlike
stateless-scoped instances, which exist only as long as a specific operation
is being processed, once a composite-scoped instance is created, it exists
until the composite instance itself goes out of scope.  One way to
consider this from a C++ view is to think about when the library containing
the class is loaded into memory.  For a stateless-scoped instance,
the runtime can load a library instance for each operation request.  But
for a composite-scoped instance, the library instance should be loaded
when the composite instance is created, a class may have static data members
(consider an in-memory database).  The component implementation itself
determines if it is stateless or not and thus the appropriate scope, but
it has no awareness of any composite(s) that may used it as a component
implementation.

We would be happy to answer any further
questions.

Bryan Aupperle, Ph.D.
STSM, WebSphere Enterprise Platform Software Solution Architect

Research Triangle Park,  NC 
+1 919-254-7508 (T/L 444-7508)
Internet Address: aupperle@us.ibm.com