Subject: HTTP/OCP: OPES-Via to replace OPES-Processor and OPES-Service

From: Alex Rousskov <[email-masked]>
Date: Fri, 24 Oct 2003 14:44:33 -0600 (MDT)

The current HTTP/OCP draft defines OPES-System, OPES-Processor, and
OPES-Service to support tracing requirements of the Communications
draft. OPES-System is mean to contain a URL that a user will access to
get high-level information about what is going on. The OPES-Processor
and OPES-Service headers are to specify OPES agents that touched the
application message.

OPES processor and service are not a well-defined thing. A processor
can be a service at the same time, and vice-versa. It is possible that
there will be a third kind of entity that would need to be traced in
the future (proxylet or whatever).

Having two headers makes it impossible to determine the order of
agent invocations. Was the second processor or the second service
applied first?

Header names are singular but may contain multiple agent entries.

To solve all of the above problems, I suggest that we use a
single, more general header: OPES-Via.

I will make documentation changes unless there are objections or
better ideas.

Alex.

P.S. OPES-System is not perfect either, especially given the
     fact that there could be two systems applied to the
     same message. In that case, there is no way to match
     OPES-Via entries with OPES-System entries.

     We could put everything into OPES-Via, I guess, but that
     would make it more difficult for end-user to troubleshoot.
     One the other hand, do we really expect dumb end-users
     to trouble shoot (the smart ones will figure it out)?