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Re: Core versioning issues and nits

From: Geoffrey M. Clemm <geoffrey.clemm@rational.com>
Date: Sun, 4 Feb 2001 16:50:11 -0500 (EST)
Message-Id: <200102042150.QAA19657@tantalum.atria.com>
To: ietf-dav-versioning@w3.org

   From: "Lisa Dusseault" <lisa@xythos.com>

   > "Why are we required to make this distinction between
   > predecessors and precursors?"

   > "Because it makes a big difference to the client whether a
   > version is in the same history as another version, in terms of
   > what you can do (for example, you cannot UPDATE a vcr to be a
   > precursor of the checked-in version, but you can UPDATE it to a
   > predecessor)."

   But the Core versioning section is supposed to be features that MUST be
   supported by all versioning servers.

There are a variety of conditionals in core.  For example,
auto-versioning behavior happens only if the DAV:auto-version
property is set, and a server is allowed to refuse to let
a client modify the value of DAV:auto-version.

   Yet, the original paragraph implies that "precursor-set" and the
   "initialize-precursor" condition aren't required to be implemented
   because it says "if the destionation of the COPY supports the
   DAV:precursor-set property".

Yes, but having certain behavior (i.e. setting the DAV:precursor-set)
happen only if the resource supports it is consistent with the
way the rest of core is defined (i.e. auto-versioning happens only
if DAV:auto-version is set).

   Also, your explanation refers to UPDATE, which is not part of core.

OK, so another difference is "the DAV:predecessor-set versions
of a version MUST show up in a DAV:version-history report containing that
version, while the DAV:precursor-set versions MUST NOT show up
in a DAV:version-history report containing that version.

   Frankly, it looks like "precursor" support is yet another option, or
   part of the UPDATE option.  It's important for the client to know if
   it's supported or not (to know whether an missing/empty value of
   precursor-set is meaningful or not) but it's optional.  Thus, it's an
   option.

If you want to know whether the property is supported by a given
resource, you can use the DAV:supported-live-property OPTIONS
request.  If it is supported, then a core versioning server
MUST set it whenever there is a copy into that resource.

Again, this is no different from auto-versioning behavior.  You
have to check the DAV:auto-version property of a resource to
know whether or not it will have the auto-versioning behavior
defined in core.

Cheers,
Geoff
Received on Sunday, 4 February 2001 16:51:12 GMT

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