Re: Xref and relaying agents (was: Protocol changes in draft-allbery-usefor-usepro-00)

["Charles Lindsey" <[e-mail]>]

In <[e-mail]> Russ Allbery <[e-mail]> writes:

>Charles Lindsey <[e-mail]> writes:
>> Russ Allbery <[e-mail]> writes:
>>> Charles Lindsey <[e-mail]> writes:

>>>> 20. [00] (3.5) Relaying agent MAY add a new Xref header.

>>> Because the same piece of software also implements a serving agent,
>>> which has to add the Xref header, and the same code path is used for
>>> all articles received by the server whether they are for further
>>> relaying or local serving.

>> Well if that is the case it was nominally the serving function that
>> added the Xref (section 3.6).

>No, because changes made by serving agents would only be seen by posting
>agents.  Serving agents do not sent messages to any other news server.
>Only relaying agents do that.

Ah! I see! We carefully said that the order of the steps in the various
"Duties" sections could be varied so long as the final effect was the
same, but we omitted to say the same for the order in which serving and
relaying were done.

You could cover it in the definitions section 1.4 by saying:

'A "relaying agent" accepts articles from injecting agents, serving
agents, or other relaying agents and distributes them ...".'

possibly with corresponding tweaks in the varius "Duties" sections.

My problem was with your wording under Duties of a Relaying Agent where
you said:

9. It MAY delete any Xref header field present and MAY add a new Xref
header field with any valid content. ...

That will be confusing to a reader who has not spotted the subtlety of the
particular order of happenings that we have described, and he will ask
himself "of what possible use is an Xref header added by a _relaying_
agent?". And of course the answer is "none" because it was not really the
relaying agent that you had in mind, but just an artefact of the way
things were described.

I think the simplest thing is to admit that relaying agents may obtain
their input from serving agents, as I have suggested above, and then that
Step 9 for relaying agents can be reduced to a simple "MAY delete XREFs".

>> Now whether such an agent first stores the article and then relays what
>> it has stored, or whether it relays first and then stores after is none
>> of our business.

And so our document should reflect that.

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