# Re: mid and cid URLs

Ned Freed (NED@innosoft.com)
Tue, 21 Nov 1995 22:33:31 -0800 (PST)

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    Date: Tue, 21 Nov 1995 22:33:31 -0800 (PST)

    From: Ned Freed <NED@innosoft.com>

    Subject: Re: mid and cid URLs

    In-Reply-To: "Your message dated Tue, 21 Nov 1995 16:42:47 -0500 (EST)"

    To: asg@severn.wash.inmet.com

    Message-Id: <01HXX6XEA39Y9BWNBV@INNOSOFT.COM>

> 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.

Its certainly possible... Its also possible for a message to have a bunch of
message-ids and a bunch of content-ids, associated with a set of parts that
don't overlap.

This needs to be clarified in Ed's draft, I believe. When a content-id is
qualified with a message-id, which message-id is it qualified by? The outermost
one on the entire message seems logical and its what I would choose, but I can
come up with cases where its not the right choice. For example, suppose you
have a message that contains a bunch of different drafts of the same message,
each draft having the same content-ids but different message-ids. This is
admittedly a contrived example, but it illustrates the sorts of concerns
qualification leads to.

For that matter, the issue of whether or not nested message-ids can be referred
to needs to be addressed.

> 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.

This doesn't change the fact that there's going to be a separate database
of content-ids and message-ids to search.

> 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.

One problem with this is there are no reference counts to insure that a given
chunk of content will be retained. This is a fact of life with messages stores,
which typically have very high content turnover rates.

Ned

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