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RE: Versioning goals doc

From: David G. Durand <dgd@cs.bu.edu>
Date: Mon, 28 Sep 1998 14:51:51 -0400
Message-Id: <v03007801b235870373ca@[]>
To: WEBDAV WG <w3c-dist-auth@w3.org>
At 12:04 PM -0400 9/28/98, Jim Whitehead wrote:

>One of my major concerns with a change-oriented approach is that it tends to
>assume the system has a lot of content-type-specific knowledge, and it tends
>to assume you're dealing with text-like objects.  This is contrary to one of
>the underlying design principles of the Web, which is that operations are
>media-type independent.

I have three reactions to this:

One is to agree with Sankar's points. (But I'll actually belabour them a
bit in my own words)

The second is to point out that any object stored in a computer can be
treated as a sequence of octets, and changes to those sequences are
_always_ a possible, if sometimes far from optimal, way to represent
changes. So, on the face of it, your assertion is (trivially) false.
"Text-like objects" is a term that makes a fundamental fact of computer
encoding look like special pleading for a favored data format.

The third is to say that the notion of sequence of characters is in fact a
significant special case deserving of meaningful treatment (as, for
instance the MIME standard's attempts to provide useful rules for the
text/* types). So, even if you don't believe my argument that there is no
special pleading for text, I think that there's a very good claim that such
special pleading is legitimate anyway. The possible need (or desire) for
content-type-specialized change formats is a separate issue, and has
exactly nothing to do with the accomodating change-set style versioning,
especially given the existence of a lowest-common-denominator chnage
format. There are many possible ones that would work for arbitrary octet
sequences (as for instance, the as yet unreleased VTML 2.0).

Even for text, there is a lot to be said for an octet-sequence approach,
given the variety of modern character encodings. I can think of
single-octet character codes, varying length codes like UTF-8, 16-bit
codes, 16-bit codes plus the use of "surrogate characters" to map pairs of
16-bit characters to a larger portion of the ISO character space. And
someone somewhere will evantually want some other variation for some

   -- David

David Durand              dgd@cs.bu.edu  \  david@dynamicDiagrams.com
Boston University Computer Science        \  Sr. Analyst
http://www.cs.bu.edu/students/grads/dgd/   \  Dynamic Diagrams
--------------------------------------------\  http://www.dynamicDiagrams.com/
MAPA: mapping for the WWW                    \__________________________
Received on Monday, 28 September 1998 14:44:29 UTC

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