Martin,
> But I do not understand why it is an absolute requirement to have a
> keep-alive message in order to create a working callout protocol.
> And I am missing your arguments for this position. Andre and you
> tell me about "less efficient" and "it complicates without...".
> These are not arguments for a MUST, are they?
If the goal would only be to have some "working" mechanism for remote
service execution, you could probably do this with already existing
mechanisms - a callout protocol is somehow motivatate by
efficiency/complexity considerations, so I'd assume it's fine to have
some requirements with respect to those issues.
-Markus