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Re: Issue: Locking namespaces vs. resources

From: Jason Crawford <ccjason@us.ibm.com>
Date: Fri, 25 May 2001 00:25:45 -0400
To: "Eric Sedlar" <eric.sedlar@oracle.com>
Cc: "WebDAV WG" <w3c-dist-auth@w3.org>
Message-ID: <OF6C335654.38944513-ON85256A57.00147737@pok.ibm.com>

There was a long discussion of locking a URL (so that a resource can't
move when locked) in the fall of 1999, and in looking back through the
archive, I didn't get a feeling of resolution that the spec should be
changed in any way.
We didn't resolve it, but we were close.  In Dec 99 the locking discussion
got defered as some of the advanced collections issues were suddenly hotly

from Yaron, and there were a number of proposals to actually specify
whether you wanted a namespace lock or a resource lock, rather than
leaving this vague.  I still think this is very useful, for performance
I assume people tend to lock resources because they want to work on them
and modify them.  I can't imagine one wanting to allow folks the resource
they are working on unless... (1) moving it doesn't prevent them from being
able to "check their modifications in".   Or (2) they know there is no one
that will move it.  How common are these?  Are there other cases?

 (I think Greg Stein mentioned that mod_dav must recursively
search the source directory for locks before doing a MOVE for just this
reason--not a good thing)
I think there is an alternative algorithm that can be used whereby locking
marks the bindings between the locked resource and the root resource
of the namespace.  The cost of marking/unmarking should be O(log(n)) where
n is
the number of resources in the system.   The cost of checking before
a binding should be O(1).  In other words, not expensive if this algorithm
can be used.   Is there a problem doing this?  It doesn't sound expensive.

Received on Friday, 25 May 2001 00:26:43 UTC

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