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Re: idempotent POSTs

• To: xml-dev@l...
• Subject: Re: idempotent POSTs
• From: "Thomas B. Passin" <tpassin@c...>
• Date: Thu, 25 Apr 2002 19:03:56 -0400
• References: <NDBBLNCOMCPLKABNJBLKIEIHFMAA.ramin@w...>

[Ramin Firoozye]

> Actually, even if you do a GET to the database, if it goes through an
> intermediary function (like a servlet) it will end up changing the
resource.
> The logging business changing state is a side-issue which gets you into
> Schroedinger's Cat-like spaces (:-)
>
> Almost any application-based web-site uses GET to invoke backing code, be
it
> CGI-BIN, Servlet, JSP, ASP, CML, etc. And *that* code has lots of
> side-effects in both modifying state and invoking code that modifies
state.
>
> The original intent behind the idempotence of GET made sense when
resources
> were limited to documents. But in an application-based environment, GET
and
> PUT have become shorthands for 'short' vs. 'long' CALL frames, where
> GET-based requests are limited to URL size and PUT is not.
>
Well, I somewhat agree with you about the state of the practice.  I worded
what I said fairly carefully to refer to decouple the idea of "idempotent"
from most of the other stuff (at least I thought I did).  Still, just
because I use cgi or Cold Fusion or Zope or whatever do create a response
doesn't necessarily mean that the resource has been changed by virtue of
state information having changed on the server.

Cheers,

Tom P

>
> > -----Original Message-----
> > From: Thomas B. Passin [mailto:tpassin@c...]
> > Sent: Wednesday, April 24, 2002 9:44 PM
> > To: xml-dev@l...
> > Subject: Re:  idempotent POSTs
> >
> >
> > [Jeff Greif]
> >
> > Just to take issue with this one specific point:
> > >
> > > 2.  GET is not actually idempotent, owing to the nearly
> > ubiquitous process
> > > of logging the request URI, including any attached query.  This
clearly
> > > modifies server state and sometimes causes security and/or privacy
> > concerns.
> > >
> >
> > Logging the request does not change the state of the specific
> > __resource__,
> > even though it does change the serve state.  The side effects
> > referred to by
> > idempotent/non-idempotent are, as I have understood it, about
> > changes to the
> > resource itself.  For example, if you GET data from a database,
> > the database
> > contents that go into the response are not supposed to change, so that
you
> > would get the same data back.
> >
> > It can get a bit confusing, not because the log modifies serve state,
but
> > because what is the "data", anyway?  If I redesign the page but return
the
> > same values from the database, is it just another representation
> > of the same
> > "resource"?  The intent is surely "yes", but it's always possible to
argue
> > grey areas.
> >
> > Cheers,
> >
> > Tom P
> >
> >
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• References:
  • RE: idempotent POSTs
    • From: "Ramin Firoozye" <ramin@w...>

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