DR600: Transport Neutrality

DR600 states:
	"The XP specification must not mandate any dependency on specific
features or mechanisms provided by a particular transport protocol beyond
the basic requirement that the transport protocol must have the ability to
deliver the XP envelope as an whole unit. This requirement does not preclude
a mapping or binding to a transport protocol taking advantages of such
features. It is intended to ensure that the basic XP specification will be
transport neutral."

I like this requirement, however I also think that it contains an
implication that may prove problematic with respect to 'synchronous'
request/response interactions such as the use of POST in the SOAP/HTTP
bindings to enable the correlation of requests and responses in RPC
invocations.

For straighforward unidirectional XP message delivery this requirement is
fine. However, for matching 'synchonous' request/response pairs I think this
requirement implies either:

a) the existence of a transport independent mechanism 'addressing' responses
and for matching request response pairs (ie. one that works say over SMTP as
a transport as well as HTTP).

	or

b) a transport specific mechanism for 'addressing' responses and matching
request/response pairs that gets pushed downward into the definition of a
transport binding for a given 'transport protocol'.

I think that if neither of these holds then we loose the neutrality this
requirement is intended to "ensure".

Have I missed something?

Regards

Stuart Williams

Received on Tuesday, 14 November 2000 11:26:42 UTC