# Re: mid and cid URLs

Al Gilman (asg@severn.wash.inmet.com)
Tue, 21 Nov 1995 16:42:47 -0500 (EST)

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    From: asg@severn.wash.inmet.com (Al Gilman)

    Message-Id: <9511212142.AA07236@severn.wash.inmet.com>

    Subject: Re: mid and cid URLs

    To: NED@INNOSOFT.COM (Ned Freed)

    Date: Tue, 21 Nov 1995 16:42:47 -0500 (EST)

    In-Reply-To: <01HXWLFACL0G9BWNBV@INNOSOFT.COM> from "Ned Freed" at Nov 21, 95 12:03:24 pm

To follow up on what Ned Freed said ...
<Al Gilman:>
> 1. By construction, these two nominal schemes are one scheme and we
> should only use one name for them. MID or MIDCID are possibles.
While its certainly possible to do this, I don't see why you'd want to.
Message-IDs and Content-IDs are distinct entities. A given part of a message
can have neither, one, or both of them.
I thought from Ed's construction that one was expected to cite a
Message-ID to reference a Content-ID. So I didn't expect that
one would not find an identified [part] Content in an
un-identified Message.

There is also the question of scope. I see support of message-ids as a
cross-message sort of thing, preferably implemented as an index emcompassing
the entire mailbox. (Preference would be given to whatever message is
"current", of course.) Content-ids, on the other hand,
are largely intended to
be used within a single message. It therefore seems logical to give some
indication of scope in the scheme identifier.

Defining a URI scheme gets you into a much bigger market than
that. Look at what Hypermail does to link things up from a
combination of Message-IDs, mailbox designations, and http: URLs.

If any significant traffic in CID-identified parts develops,
people will want to refer to them across wider scopes. In
particular, I would expect that enclosures to one message will be
recycled as references cited [or attached as a
message/external-body] in other messages. You only discover
after the fact that there are seven people who would be
interested in what you cooked up to tell Joe.

I guess what I'm asking is what advantage you in collapsing the schemes into
one. If there is a big one I guess I wouldn't mind making such a change.
If you wrote the code in a Web Browser that parses URIs, would you
want to add a special case for a "cid:" scheme that you would never,
in practice, see? Now, that's a small hit. But what you are
registering as a URI scheme is something a lot of people handle.
MIME implementors are not the only people affected.

Al

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