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Re: range locks vs. section locks

From: Steve Carter <SRCarter@novell.com>
Date: Fri, 21 Feb 1997 12:42:45 -0700
Message-Id: <s30d9a76.018@novell.com>
To: Mark_Day/CAM/Lotus@lotus.com, w3c-dist-auth@w3.org
I'm suprised that some people think that the reason that I've supported range locking
is because GroupWise uses the feature, GroupWise does not. In the early days
SoftSolutions did, but that is behind us. Basically, range locking is a useful method
for implementing a fixed-length record store that provides the necessary functionality
for small to medium document management systems (whether they do versioning or not).
Some editing systems that use range locking do so because they access a fixed-length
index of the document structure that provides all access to the document body. Range
locking is used here to protect the specific portion of the document. In both cases
you do not see the byte count changing except at the end of the fixed-length portion of 
the document or the DMS control file. Having been there, I suspect that there are
systems out there that use range locking to provide this type of functionality.

So now I'll put on my Novell hat. No, I don't need range locking. But I think we're being
short sighted if we think that functionality such as range locking has no value to DAV.


>>> <Mark_Day/CAM/Lotus@lotus.com> 02/21/97 08:54AM >>>

I agree with Larry that it makes more sense in most cases to talk about
section locks for the scenario of multiple authors wanting to manipulate
different parts of the document. If your locks are on byte ranges, then the
semantics (as I understand them) seem pretty unpleasant:

1. In the simplest approach, you can't change the size of the locked range
unless you lock from the start of the range to the end of the document
(thus effectively locking most of the document if what you're modifying is
near the beginning of the document).

2. In a more complex approach, you can't safely re-lock a range using the
same start & end points once you release the lock, because the actual byte
numbering of that content in the document may have changed as others have
inserted or deleted bytes from their ranges.  Section locking also has this
problem, but in a milder form: the problem arises as sections are added and
removed, which one would expect to be much less common than adding and
removing bytes.

People who have more experience with byte-locking systems should feel free
to correct me on these points if I have misunderstood.


Received on Friday, 21 February 1997 15:06:50 UTC

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