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Re: draft findings on Unsafe Methods (whenToUseGet-7)

From: Paul Prescod <paul@prescod.net>
Date: Thu, 18 Apr 2002 09:45:48 -0700
Message-ID: <3CBEF83C.6DD53D56@prescod.net>
To: Graham Klyne <GK@ninebynine.org>
CC: www-tag@w3.org
Graham Klyne wrote:
> At 12:34 AM 4/18/02 -0700, Paul Prescod wrote:
> > > - an operation that is idempotent:  has no further side effects if repeated
> > > after it has been performed once
> >
> >The HTTP specification uses the term idempotent to mean idempotent.
> >
> >http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.1.2
> >
> >PUT is safe but not idempotent.
> Yup, what it says there is exactly what I meant.  And according to that
> reference, PUT is idempotent.

Sorry, I meant to say "PUT is idempotent but not safe."

> The section immediately preceding the one you cite mentions "actions they
> might take which may have an unexpected significance to themselves or
> others" -- in a web context, it seems to me that any action which changes
> what is visible on the web is potentially significant, hence my attempt to
> characterize it in terms of visible side effects.

What if following a link on the Web had the semantic "inject patient
with drug". That may not have visible side effects but is still a
serious, dangerous side effect. Conversely, incrementing a page hit
counter is not dangerous but IS web-visible.

 Paul Prescod
Received on Thursday, 18 April 2002 12:45:03 UTC

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