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Re: is this example valid?

From: Geoffrey M. Clemm <geoffrey.clemm@rational.com>
Date: Tue, 16 Jan 2001 13:33:47 -0500 (EST)
Message-Id: <200101161833.NAA17509@tantalum.atria.com>
To: ietf-dav-versioning@w3.org

   From: Greg Stein <gstein@lyra.org>

   Sorry, I realized this after I sent the message. I want to do:

     CHECKOUT /the/baseline/selector/some/file.c
     Label: which-baseline

A baseline selector is not a collection ... it is just a resource that
you can checkout and checkin to create new baselines.

Many baseline implementations will be things like "an internal label"
or "a list of version URL's", which do not directly provide
collection semantics.

   Thus, getting a working resource for "file.c" from baseline
   "which-baseline".  This is premised on the fact that a
   baseline-selector operates just like a regular VCR, but that it
   sets up the children to come from a particular baseline.  Does this
   sound right?

A baseline-selector acts just like a regular vcr (i.e. you can
check it in and check it out), but it is not a collection so it
has no children.

   If not, then is there a way to do this? Would I have to create a new
   baseline selector, UDPATE it, then CHECKOUT/apply-to-version?

Almost.  You can create a new collection (reasonably enough, since you
do want a collection :-), and then put it under baseline control, i.e.:

MKCOL /collection/for-baseline/foo
BASELINE-CONTROL /collection/for-baseline/foo
  <DAV:baseline> /baseline/xyz34
CHECKOUT /collection/for-baseline/foo/some/file.c

Note that you can continue to use /my/collection for all your subsequent
checkouts against baseline foo ... so you only have to do the
BASELINE-CONTROL once for any checkout against that baseline.

  (I hope not because that doesn't scale as well)

For many implementations (such as the very common label-based baseline
implementation), that is the only way it will scale well, because it
tells the server when to "cache" a traversable form of the baseline,
and when to empty that "cache" (i.e. when /my/collection is deleted).

In subversion, the BASELINE-CONTROL is a trivial operation, because
your baselines are already in traversable form.  So the cost to you is
that protocol asks you to "publish" important baselines in the form of
baseline-controlled collections, i.e. give them human meaningful

I agree that the intermediate BASELINE-CONTROL step is not optimized
towards your implementation (which does not need it), but it is
needed for interoperability with most other baseline implementations.

Received on Tuesday, 16 January 2001 13:34:43 UTC

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