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[DR 702] Why compare two messages?

From: <Noah_Mendelsohn@lotus.com>
Date: Mon, 13 Nov 2000 18:15:35 -0500
To: xml-dist-app@w3.org
Message-ID: <OF84F1CCDC.0F279D8B-ON85256996.007F0D6D@lotus.com>
The proposed requirement states:

"The XP specification must define the concept of protocol evolution and
define a mechanism or mechanisms for identifying XP revisions. This
mechanism or mechanisms must ensure that given two XP messages it should be
possible, by simple inspection of the messages, to determine if they are
compatible. The specification must define the concepts of backwards
compatible and backwards incompatible evolution. Furthermore, the XP
envelope must support both optional and mandatory extensibility of
applications using the XP envelope. "

Main concern:

The sentence starting "This mechanism... must ensure that given two XP
messages..." seems to suggest that evolution is implemented as a relation
on two or more messages.  I don't think this is necessarily so.  There are
all sorts of ways to evolve protocols without there being a 1-for-1
equivalence of messages.  Furthermore, the sense in which two messages
might be "compatible" is not even defined informally.  Also, the
requirement is a bit vague on the degree to which the intention is to
ensure evolvability of XP itself, vs. protocols built using XP.

For these reasons, Lotus intends to vote that this item requires further
discussion.  Thank you.

------------------------------------------------------------------------
Noah Mendelsohn                                    Voice: 1-617-693-4036
Lotus Development Corp.                            Fax: 1-617-693-8676
One Rogers Street
Cambridge, MA 02142
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Received on Monday, 13 November 2000 18:47:31 GMT

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