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Re: [DR 702] Why compare two messages?

From: Ray Denenberg <rden@loc.gov>
Date: Tue, 14 Nov 2000 09:59:40 -0500
Message-ID: <3A11535C.546B83DC@rs8.loc.gov>
To: xml-dist-app@w3.org
I agree with Noah, and I think that the requirement should be crafted without
reference to comparing "two messages" to "determine if they are
compatible".

What I *think* we're trying to say is:

(1) XP implementation A, upon receipt of an XP message from XP implementation B,
must be able to determine -- by inspection of the message -- whether it can
process the message.
(2) When A subsequently formulates a message to send to B, there must be a
mechanism for A to determine -- by inspection of the message from B -- whether
B can process the message it proposes to send.

Is this basically what we're trying to say?

--Ray


Noah_Mendelsohn@lotus.com wrote:

> 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
> ------------------------------------------------------------------------

--
Ray Denenberg
Library of Congress
rden@loc.gov
202-707-5795
Received on Tuesday, 14 November 2000 09:59:08 GMT

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