Subject: Re: DIFF method

From: Geoffrey M Clemm <[email-masked]>
Date: Mon, 20 Mar 2006 08:11:08 -0500

The only interesting thing aobut a DIFF method is the format of its 
result.
There was such a wide variation in the different formats that diff tools
use for different types of resources that it didn't appear to be something
on which we could get consensus.  There are some standards for diff 
formats,
e.g., http://www.ietf.org/rfc/rfc3284.txt?number=3284 (The VCDIFF Generic
Differencing and Compression Data Format) and some new ones being
proposed, e.g., 
http://www.ietf.org/internet-drafts/draft-ietf-simple-xcap-diff-03.txt

Cheers,
Geoff

Werner wrote on 03/20/2006 04:28:34 AM:
> Shouldn't there be a DIFF method? Calculating the difference between
> two versions may be a very specialised operation for some document
> formats. The software or resources to accomplish it may not be available
> to clients.

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From: Werner Donné <[email-masked]>
Date: Mon, 20 Mar 2006 14:24:55 +0100

Geoffrey M Clemm wrote:
> 
> The only interesting thing aobut a DIFF method is the format of its result.

The diff calculation itself can require software that can't be distributed
to clients, because of licensing limitations, programming language, resources
or whatever. Note that it can be more than just a diff of text files. I
will use DeltaXML, for example, which is specialised in calculating the diff
between two XML documents. It inserts mark-up in its own namespace in the
resulting document.

The format can also be converted on the fly, depending on the "Accept"
request header. I could convert it to PDF, again with tools that are only
available on the server.

> Geoff

Regards,

Werner.

-- 
Werner Donné  --  Re
Engelbeekstraat 8
B-3300 Tienen
tel: (+32) 486 425803	e-mail: [email-masked]

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From: Geoffrey M Clemm <[email-masked]>
Date: Mon, 20 Mar 2006 08:37:11 -0500

I wasn't questioning the desirability (from a client's perspective) of
having a DIFF method, but was just pointing out that the challenge is
to come up with a standard result format that more than one server will
be willing/able to produce.

Cheers,
Geoff

Werner wrote on 03/20/2006 08:24:55 AM:

> Geoffrey M Clemm wrote:
> > The only interesting thing about a DIFF method is the format of its 
result.
formats,

---

From: Werner Donné <[email-masked]>
Date: Mon, 20 Mar 2006 14:46:57 +0100

> be willing/able to produce.

I don't see why there should be a standard result format. There are by
definition many, because there are many content types. For some a diff
may even not be possible. There can also be several result formats
for the same content type. That is a matter of representation.

Regards,

Werner.