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Terminology of error-oloy
- To: KMP@MIT-MC.ARPA
- Subject: Terminology of error-oloy
- From: "Daniel L. Weinreb" <DLW@SCRC-STONY-BROOK.ARPA>
- Date: Mon, 15 Oct 84 14:54 EDT
- Cc: cl-error-handling@SU-AI.ARPA
- In-reply-to: The message of 13 Oct 84 19:24-EDT from Kent M Pitman <KMP at MIT-MC>
Your summary of the terminology is good. Jan Walker and I established
the terminology while she was editing the document, and the word "event"
was introduced because it really turned out to be necessary to have a
word for that concept in order to be accurate and clear at the same
time. You'll notice that the word "event" is hardly ever used after the
first few pages, which explain the fundamental concepts of the condition
mechanism. It might turn out to be useful in this discussion; in any
case, it's likely that its meaning will be clear from context.
The exact definition of what constitutes an "error" is something that
has eluded me for a long time. If a program has a bug such that it
computes the wrong result, but at no time actually signals anything,
then it has violated its contract and therefore is in error
nevertheless. It can also be argued that if (/ 1 0) signals the
sys:divide-by-zero condition, then it was operating properly and
according to its contract, and therefore no error occurred. On one
hand, I'd be happy to see a good resolution of these issues. On the
other hand, it's probably a philosophical can of worms that need not be
opened in order for us to proceed. I just thought I should mention that
there doesn't seem to be a completely good definition of "error".
One thing that we should all agree to is that an error is a synchronous
event; that is, it happens as a direct result of the execution of a
program, and it happens at a particular point in that program. The
occurrance of an asynchronous event, like an interval timer going off,
or a network connection being broken due to a timeout, or any kind of
asynchronous "interrupt", is not an "error" in the sense we mean here.