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Deconstructing DS7

From: Frank DeRose <frankd@tibco.com>
Date: Wed, 31 Jan 2001 15:44:09 -0800
To: <xml-dist-app@w3.org>
Message-ID: <OFELJFDBDMKCBMENENFOIEENDDAA.frankd@tibco.com>
It's unclear to me what message exchanges are implied by DS7. I see 2
alternative interpretations (probably because I don't know anything about
blind auction marketplaces):

[Note that I've kept the term "intermediary" throughout this discussion, but
please substitute "broker" or "service" or whatever word you like for it.]

Interpretation1
1.) The exchange between the buyer and the intermediary consists of 1
message from the buyer to the intermediary and 1 message from the
intermediary back to the buyer.
2.) For each seller s, the exchange between the intermediary and s consists
of 1 message from the intermediary to s and 1 message from s back to the
intermediary.

Under this interpretation, one could argue that DS7 is simply a
"composition" of instances of DS3 or DS4 glued together by workflow. Of
course, this would imply that all the exchanges between the intermediary and
the sellers take place before the intermediary sends the response back to
the buyer. But, this is all hidden from the buyer. From his point of view,
he just sends off a request and gets back a reply. Likewise, for each
seller, the intermediary just sends off a request and gets back a reply.
Just like DS3 or DS4.

Alternative2
1.) The exchange between the buyer and the intermediary consists of 1
message from the buyer to the intermediary and 1 message FOR EACH SELLER
from the intermediary back to the buyer.
2.) Same as with Alternative1.

Under this interpretation, the exchange between the buyer and the
intermediary consists of a request followed by "multiple partial replies."
Maybe we need to treat this pattern as a separate scenario ("multiple
partial replies scenario"). But, the exchanges between intermediary and
seller still are examples of DS3 or DS4 and are again hidden from the buyer.
Under this interpretation, DS7 would still seem to be a composition of other
sub-scenarios glued together by workflow.

Also, the word "broadcast" is used to describe how the intermediary sends
requests to the sellers. Again, I see 2 alternative interpretations:

Interpretation1
Use of a "broadcast" or "multicast" transport is implied. Binding XP to a
broadcast/multicast transport should be broken out as a scenario on its own.
Please note that this doesn't imply that we need to add multicast/broadcast
support to XP itself, but only that it should be possible to bind XP to such
a transport.

Interpretation2
No information about the transport should be inferred. The word "broadcast"
is simply used to describe the fact that there are DS3 or DS4 exchanges
between one intermediary and many sellers.

Frank DeRose
TIBCO Software Inc.
3165 Porter Dr
Palo Alto, CA 94303
650-846-5570 (vox)
650-846-1267 (fax)
frankd@tibco.com
www.tibco.com
Received on Wednesday, 31 January 2001 18:42:11 GMT

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