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From: steve%cs.ucl.ac.uk@BRL.ARPA (Steve Kille)
Newsgroups: net.mail.headers
Subject: Re: Distribution lists
Message-ID: <2632@brl-smoke.ARPA>
Date: Tue, 29-Jul-86 04:37:41 EDT
Article-I.D.: brl-smok.2632
Posted: Tue Jul 29 04:37:41 1986
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         From:    Jacob_Palme_QZ@qzcom
         Subject: Distribution lists
         Date:    26 Jul 86 13:30 +0200


         HIER is the method commonly used in INTERNET. The restriction
         requiring a hierarchical structure will make message transmission
         slower and less efficient in some cases.

         In some cases it is
         natural to allow every list to be a member of every other list
         in a set of linked lists.

I dispute this last sentence.   I agree that there is a loss of
generality.   However, I would suggest that the convoluted
structures prohibited are undesirable, and that prohibiting them
is an advantage.  I can see a few cases where there would be a
need to create an 'invisible' list purely for the purposes of
structuring, but not where this would get out of hand.

I suggest a lemma (I don't have time to figure out a proof),
that ANY list structure can be represented by HIER.

As a challenge, I request REAL examples of list structures for
which HIER is inappropriate.   I suggest is is EXACTLY what is
wanted in the majority of cases, and is quite reasonable in
all others.   If this suggestion is correct, it makes HIER an
interesting choice of loop control.

Steve