Changeset 657

Timestamp:

Jul 29, 2009, 4:27:37 AM (10 years ago)

Author:

fielding@…

Message:

Resolve #27: fix definition of idempotent

File:

• draft-ietf-httpbis/latest/p2-semantics.xml (modified) (1 diff)

draft-ietf-httpbis/latest/p2-semantics.xml

@@ -690 +690 @@
 <iref item="Idempotent Methods" primary="true"/>
 <t>
-   Methods can also have the property of "idempotence" in that (aside
-   from error or expiration issues) the side-effects of N &gt; 0 identical
-   requests is the same as for a single request. The methods GET, HEAD,
-   PUT and DELETE share this property. Also, the methods OPTIONS and
-   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
-</t>
-<t>
-   However, it is possible that a sequence of several requests is non-idempotent,
-   even if all of the methods executed in that sequence are
-   idempotent. (A sequence is idempotent if a single execution of the
-   entire sequence always yields a result that is not changed by a
-   reexecution of all, or part, of that sequence.) For example, a
-   sequence is non-idempotent if its result depends on a value that is
-   later modified in the same sequence.
-</t>
-<t>
-   A sequence that never has side effects is idempotent, by definition
-   (provided that no concurrent operations are being executed on the
-   same set of resources).
+   Methods can also have the property of "idempotence" in that, aside
+   from error or expiration issues, the intended effect of multiple
+   identical requests is the same as for a single request.
+   The methods PUT, DELETE, and all safe methods are idempotent.
+   It is important to note that idempotence refers only to changes
+   requested by the client: a server is free to change its state due
+   to multiple requests for the purpose of tracking those requests,
+   versioning of results, etc.
 </t>
 </section>