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References with multiple precursore (was Attempts at establishing harmful conventions)

2005-01-11 10:12:24

In <200501100920(_dot_)17864(_dot_)blilly(_at_)erols(_dot_)com> Bruce Lilly 
<blilly(_at_)erols(_dot_)com> writes:

On Thu December 2 2004 18:58, Steve Dorner wrote:
At 8:27 PM +0200 12/2/04, Kai Henningsen wrote:
 > For that matter, how many permit a user to select multiple
 messages to compose a response citing all of the selected
 messages (including appropriate setting of In-Reply-To and
 References fields)?

Hopefully few, as there *is no* appropriate setting for those fields in 
that situation.

We actually hashed out a way that seemed right enough on this list a 
year or so ago.

There was a discussion in June 2003, however if it can be
said to have reached any conclusions, I believe those
conclusions include:

[snipped list of problems]

So far, I haven't seen any detailed proposal to address the
issue in accordance with those conclusions (indeed, several
points are somewhat contradictory).

Yes, that is a reasonable summary of the problems that we found. Here is
another suggestion:

Currently, where a response has only one precursor, a discussion thread
consists of a tree, and the References header consists of the path from
the root of the tree to the message at the tip of the tree which contains
that References header.

Sometimes the path may get pruned, because its length has become
excessive. And sometimes implementations botch it in various ways, or even
omit it entirely. But by and large it is well understood, and MUAs manage
to display threads more or less OK.

If you want to extend that to responses to multiple precursors, then the
tree becomes a DAG (Directed Acyclic Graph), and there are many possible
paths from the root to each tip, and there is no way for the References
header to represent that situation. Moreover, inventing new syntax for the
References header leads to compatibility problems.

So here is a suggestion to get around the problem in a way that will
probaby allow existing MUAs to do a reasonable job:

Simply allow there to be multiple occurrences of the References header in
each message - one for each path from the root to the tip in question.

Then an updated MUA can look at them all, and has full information
available to give the best possible presentation. Meanwhile, an unupdated
MUA will probably just take the first, or the last, or a randomly chosen
one, and will at least produce a plausible thread.

And it is not actually necessary for the whole of each of the various
paths to appear in the various References headers. Just the segment that
differs from the others should suffice, though careful thought would have
to be given to defining exactly what the rule should be.

Charles H. Lindsey ---------At Home, doing my own thing------------------------
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