On Thu, 10 Apr 2003, The Purple Streak, Hilarie Orman wrote:
I had a returned thought on the issue of whether or not data had to
complete the loop between the OPES processor and the callout server.
If the proxied protocol is a store-and-forward type, like SMTP, then
it seems that the callout server might, quite properly, send
transformed messages directly to an application endpoint (SMTP server)
without going back through the OPES processor.
If this is proper, should we document it. If it is improper, can
we say why?
Excellent question!
If a callout server accepts application message and then just forwards
an adapted version elsewhere, it is not (should not be) a callout
server. It is an OPES processor! Thus, it is absolutely proper to do
that as long as the entity in question does not pretend to be a
callout server and obeys all processor requirements.
Here is what you get in that case:
-- (SMTP) --> OPES --> (SMTP) --> OPES --> (SMTP)
processor 1 processor 2
Which is perfectly fine and is obviously beyond OCP scope (OCP is
not involved here).
If, for some unnatural reason, the same thing is implemented using
OCP, it may still be OPES-legal as long as both OPES agents know what
they are doing:
callout server
-- (SMTP) --> OPES --> (OCP) --> _and_ OPES --> (SMTP)
processor 1 processor 2
Essentially, "adaptation service" here means "I took care of it,
forget it". This is OK as long as processors cooperate. Note that the
callout server would be required to respond with that "I took care of
it" application message to its OPES processor 1 (that application
message/response will probably have no payload though, just metadata).
No need to documented this convoluted case, IMO.
A somewhat similar but more realistic example with an "I took care of
it" response would be a "black hole" service (e.g., a SPAM filter):
-- (SMTP) --> OPES --> (OCP) --> callout
processor 1 server
The latter might be worth documenting in an "SMTP adaptation using
OPES" draft.
HTH,
Alex.