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Subject: RE: oops [ebxml-cppa-negot] NDD Schema and Sample NDD instancedocumen t
- From: Dale Moberg <dmoberg@cyclonecommerce.com>
- To: Martin W Sachs <mwsachs@us.ibm.com>,"Kartha, Neelakantan" <N_Kartha@stercomm.com>
- Date: Mon, 30 Sep 2002 14:14:41 -0700
Issue of using Draft CPAs and CPA
templates
It seems that there are two related, although slightly
different
approaches now on the table. Let me first describe them. To start
with,
Party A has CPP_A and and NDD_A that points to CPP_A. Party B has CPP_B
and
NDD_B that points to CPP_B.
MWS: One immediate problem is that the
CPPA specification permits
publishing CPA template instead of a CPP. I
believe that this means that we would
have to provide "Approach that Marty
proposed" even if we agree to include
Kartha's approach.
I favor Negotiation version 1.0
using either CPA templates or draft CPAs
as the starting point for
negotiation. This puts CPA template and
draft CPA formation outside the
Negotiation process in a prior
phase called CPA "Formation".
And prior to this phase, is a discovery
phase of CP P [edited] s or maybe CPA templates. The draft CPA
can be
a product of merging CPPs or
filling out a CPA template. A CPA
template would be a product of
merging CPPs or maybe just
filling out an
industry/vertical/consortium approved pattern for
the templates (this would be like a
CPA template but leaving
open both sides Endpoint information,
PartyId and Role choices, etc)
Approach I proposed:
1. Party A and Party B
negotiate on elements that are in the CPP and come
to an agreement on
them. NDD_A and NDD_B are used during this process.
MWS: CPP-A and CPP-B also have to be used in this
process.
MWS: One possible problem here is that because there is no
CPA template at
this stage, everything that is negotiable in both CPPs have
to be
considered during this part of the negotiation process. Composing
a CPA template
first mechanically resolves all negotiable items that can be
resolved by simple
matching between the two CPPs and extracting the
commonalities. See the
discussion in the CPA composition appendix of
the CPPA spec.
I think that Kartha's negotiation procedure
should be considered
at a future version for negotiation.
2. One of the parties (say party A) now makes a CPA template that
contains
the agreed upon values produced in step 1, as well as elements that
are
specific to the CPA (such as start, end etc.). Party A also produces an
NDD1_A, that points to
the CPA template. Note that NDD1_A does *not* refer to
the elements of the CPP,
since they already have been negotiated and agreed
upon. NDD1_A only points to the CPA
specific elements in the CPA template.
Note however that the negotiability
requirements thatmay be put in NDD1_A
might depend on the first negotiation.
3. Consequently Party B also
produces a similar NDD1_B template.
MWS: Rather than working with
two separate NDDs at this stage, I think it
would be easier to produce a
single NDD that refers to the draft CPA
template and incorporates both
parties' requirments on the CPA-only elements. The
process of composing
that combined NDD would detect any incompatibilities.
I asked Marty about how to handle the two
NDD situation a couple
of weeks ago and he indicated we better make
it a post December
effort. For the moment, the second party can
introduce its
NDD by rejecting the first Negotiation
session and then starting
a new one. Possibly not the most elegant but
workable, I think
4. Party A and B negotiate on the elemtns that
are in the CPA template and
come to an agreement on them. NDD1_A and NDD1_B
are used in this process.
Approach that Marty proposed:
1. Party A
composes a preliminary CPA template using CPP_A, CPP_B, NDD_A
and NDD_B. In
this CPA template, party A also inserts any CPA specific element like
start,
end.
I don't think Marty et al have been
requiring two NDDs.
2. Party A now produces a new NDD (call it NDD_1_A_B) that expresses
its
own and Party B's negotiability requirements.
3. A and
B then negotiate and come to agreement using NDD_1_A_B
A few
remarks and questions:
1. A simple implementation of my approach can
assume that that Steps 1 and
Step 4 can be negotiated independent of each
other. If we take that approach, the
information in NDD1_A and NDD1_B can be
made available at step 1 itself by
each of them pointing to some standard CPA
(such as the one available with the spec).
Note that NDD1_A and NDD1_B can
point only to CPA specific elements.
2. If as in Marty's approach an NDD
(such as NDD_1_A_B) needs to refer to
its own and the other parties
negotiability requirements, the current
schema needs to change so as to
enable it to have a pointer to negotiability
requirements of both
parties.
MWS: I don't think so. The combined NDD would refer
only to the CPA
template.
For instance, if party A wants to have
the
cardinality of an element betwen 1 and 4 (with
preference for lower
cardinalities) and party B wants to have the
cardinality of that
element
between 2 and 3 (with preference for the higher cardinalities), it
seems that
both these should be represented in the initial NDD_1_A_B. Is this the
way
you werethinking about it, Marty?
MWS: Not exactly. I was
assuming that Party A
would compose a single NDD that would encompass both
parties' requirements
to the extent that the other party's requirements are
acceptable to party
A. So, for example, if (in the example above), Party A
would
state the cardinality as 1-4 and then they would negotiate. Or,
Party A
could state an enumeration as the inclusive OR of both parties'
requirements on
that enumeration. Of course, since Party A is making
the initial offer, Party A
would exclude from the NDD any constraints that
are unacceptable to Party
A.
MWS: The approach that I suggested
gives the party making the initial
offer has some advantage over the other
party, which could be good or bad.
Dale: I previously noted that, in effect,
proposer has an advantage
because proposer sets the terms (NDD). A
purer peer-to-peer
perspective would permit the
other side to put forward its NDD.
A more dynamic approach could allow NDD
change during Negotiation.
I think we were near agreement on putting
these out of scope for
December. Not that there is anything wrong,
just that we have doubts
about finishing up the specification for all
this functionality.
In addition, because people are a little
concerned about the
supposed complexity of CPPA, it might be to
our advantage
to keep the feature set under control at
this point so that people
see it as easier to
implement...
The good part is that by initially filtering out the unacceptable parts
of
Party B's requirements, the negotiation may proceed more rapidly. This is
in addition
to the advantage that the CPA template composition process
converges all
negotiable items that can be resolved by simple
matching.
MWS: I believe that "Marty's approach" is already implicit in
some aspects
of the work that has been done on the BPSS and negotiation
messages, so it will be
important to discuss and resolve the differences
between the too approaches
fairly quickly.
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