Subject: Erroneous but valid APL/J, (Transpositions)
From: Ian Shannon <ishannon@airmoon.epa.nsw.gov.au>
Date: Mon, 19 Jun 1995 16:06:28 +1000

This item was in the
comp.risk
news group.

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Date: Mon, 5 Jun 95 22:33 MET DST
From: erik@kroete2.freinet.de (Erik Corry)
Subject: Compuserve addresses and a sparse name-space

Don Faatz relates that his boss regularly gets E-mail at his Compuserve
account that is destined for somebody else whose account differs by only
digit.

This is another case of a namespace not being sparse enough.  It is too
simple to hit another real Compuserve address by hitting one wrong number.
The risk could be reduced with checksum digits like those used for ISBN and
credit card numbers. Other small-namespace culprits include the telephone
system (especially when used by semi-automated systems like faxes) and some
computer languages (changing a random piece of punctuation in a C program
has a chance of resulting in a different, valid program. APL is probably
much worse.)

To make matters worse, he probably has to pay for the incorrectly sent mail
(I have heard this is how Compuserve works, but am not sure).

Erik Corry, Freiburg, Germany, +49 761 406637 erik@kroete2.freinet.de

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J would be just as likely (if not more so) to produce an erroneous but still
valid program.

farewell
ian

Ian Shannon, Metropolitan Air Quality Study
Environment Protection Authority NSW (EPANSW)
66 Rickard Road          ph:     +61 2 795-5059
Bankstown, NSW 2200      Fax:    +61 2 649 8768
Australia                email:  ishannon@airmoon.epa.nsw.gov.au
    Pythagorus was one side short of a square.

