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   RE: [xml-dev] idempotent POSTs

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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.


> -----Original Message-----
> From: Thomas B. Passin [mailto:tpassin@comcast.net]
> Sent: Wednesday, April 24, 2002 9:44 PM
> To: xml-dev@lists.xml.org
> Subject: Re: [xml-dev] 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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