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idempotence of POST

From: Larry Masinter <masinter@parc.xerox.com>
Date: Wed, 18 Sep 1996 18:58:01 PDT
To: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
Message-Id: <96Sep18.185801pdt."2733"@golden.parc.xerox.com>
In a discussion on html-wg@w3.org, the topic of GET vs. POST for
sending form data was discussed. There are two issues:

-  GET does not (at least in implementations) support a body
-  POST requests are assumed to not be 'reload'able safely without
       asking the user

There are applications for requests that have a message body but are
idempotent, e.g., a search with a complex form where the form data is
too long to encode in a URL, or in which multipart/form-data is a more
appropriate encapsulation.

There are three suggested ways of accomplishing this:

a) allow GET to take a body
b) add a new method, GET-with-body (spelled how you like)
c) allow the return value of POST to indicate that the request
   can be repeated safely.

(a) is an incompatible protocol change, at least for most
implementations.
(b) requires HTML forms that wish to request this action to
say so directly, and so is also an incompatible change for HTML, if
not for HTTP
(c) is backward compatible.

I don't know what syntax could be used with (c); it would have to be
implemented by both browsers and servers before it would be useful,
though.

Is this worth pursuing?

Larry
Received on Wednesday, 18 September 1996 19:02:14 EDT

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