Author: ts
Date: Tue Feb 26 13:00:48 2008
New Revision: 7449
Log:
- Added more information about entity tags.
Modified:
trunk/Webdav/design/design-1.1.txt
Modified: trunk/Webdav/design/design-1.1.txt
==============================================================================
--- trunk/Webdav/design/design-1.1.txt [iso-8859-1] (original)
+++ trunk/Webdav/design/design-1.1.txt [iso-8859-1] Tue Feb 26 13:00:48 2008
@@ -181,6 +181,35 @@
this includes several methods like COPY and MOVE, but also PROPFIND with a
Depth header other than 0.
+Validation
+==========
+
+The purpose of entity tags is to ensure, that a certain operation is only
+performed, if a resource resides in a certain state. This state is defined by
+an entity tag. Most likely, this applies to the GET operation in combination
+with caching for pure HTTP/1.1. However, in combination with the WebDAV
+extension, validation of entity tags might also be necessary for operations
+like PUT and others.
+
+The HTTP/1.1 RFC defines 2 different validator schemes: Strong and weak
+validators. Entity tags are generally considered strong validators, since they
+should change as soon as the affected resource changes its state. However, the
+protocol provides a way to declare entity tags to be weak validators, as
+described in the ETag header above.
+
+.. Note::
+ We should not make use of this way of weaking entity tags, but always
provide
+ the strong method.
+
+Caches (like proxy servers and browser caches) use additional methods to
+validate their content. The most common way here is to use the Last-Modified
+header in addition, which indicates the last modification time of the resource.
+
+
+-- Note::
+ We need to decide if we should support this validator in addition. This
+ would also involve more headers to react on, like If-Modified-Since. This is
+ not mandatory.
Lock support
^^^^^^^^^^^^
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