RE: [ebxml-cppa-negot] NDD Schema and Sample NDD instance documen t

[Dale Moberg <dmoberg@cyclonecommerce.com>]

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 CPAs 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.