Re: mid and cid URLs

Al Gilman (
Mon, 27 Nov 1995 11:14:39 -0500 (EST)

From: (Al Gilman)
Message-Id: <>
Subject: Re: mid and cid URLs
To: (Larry Masinter)
Date: Mon, 27 Nov 1995 11:14:39 -0500 (EST)
In-Reply-To: <> from "Larry Masinter" at Nov 26, 95 09:40:17 am

To follow up on what Larry Masinter said ...
  I've re-reviewed all of the relevant documentation (scanned all RFCs
  for the header "content-ID")  and have come to the conclusion that in
  all circumstances, 'content-ID' is required to be globally unique.
  That is, 'cid:baz@host' is always unambiguous.
  'mid:frob@host/cid:baz@host' == 'cid:baz@host'.
  In such circumstances, they wouldn't need to cite a relative URI at
I absolutely agree that they don't _need_ to.  I really think
that they should _want_ to.  The Content-ID value is
World-unique.  It is a sufficient key.  That doesn't mean that
the recipient doesn't _want_ to know that it happens to be
located in the current message.  The recipient _does_ want to
know that.

I quoted you on the matter of the CID being a sufficient key to
Harald, just now, on the ietf-types list.  

<double-negative warning>

I still think that we should not strictly limit our syntax to
carrying _only_ the information that is absolutely necessary.  I
think that we can and should define a syntax which emphasizes the
necessary information, but makes room for useful additional

Compare this with my discussion with Harald about the
advisability of annotation an MID URI for a FAQ with
"Newsgroups:" and "[archive-]Location:" info.