W3C home > Mailing lists > Public > w3c-ietf-xmldsig@w3.org > July to September 2000

Newbie comments about Canonical XML

From: Eric van der Vlist <vdv@dyomedea.com>
Date: Sat, 09 Sep 2000 17:51:20 +0200
Message-ID: <39BA5C78.9D3F0C1E@dyomedea.com>
To: w3c-ietf-xmldsig@w3.org
Hi,

After my first serious glance at the Canonical XML spec, I have a couple
of comments (I only hope they are not FAQs...):

This canonization seems to meet a very specific need.

I came to it to see if it could be used to compare XML documents and
find their differences before a CVS checkin and my first finding was
that Canonical XML is not meant to deal with standalone documents and
looses any document type information.

To say that 2 documents are identical based on the canonical output
seems pretty limitative in these conditions !

I reckon that it's meeting a need, but find that it might deserve a
mention in the abstract.

To elaborate on this point, I think that what is described here is not
so much "a physical representation, the canonical form, of an input XML
document", but rather a physical representation of an object model taken
at a given instant under given conditions (and at a given location).

Even if you have a tight control on the document you're canonizing,
since you are integrating data from external documents, you can't
guarantee that a next processing of the same document will give the same
canonical XML as these documents (or more exactly the answer to the
request for these documents) may vary.

It's may not be a problem for security applications which will require a
signature check processed on the object model (DOM or other) they are
working on, but here again, it might be worth mentioning this point
since it has an impact on the architecture to use: IMHO you can't safely
test the equivalence of two documents based on their canonical XML and
then reload the document in another tool assuming it's still
equivalent...

My 0,02 Euros

Eric
-- 
------------------------------------------------------------------------
Eric van der Vlist       Dyomedea                    http://dyomedea.com
http://xmlfr.org         http://4xt.org              http://ducotede.com
------------------------------------------------------------------------
Received on Saturday, 9 September 2000 11:50:22 GMT

This archive was generated by hypermail 2.2.0 + w3c-0.29 : Thursday, 13 January 2005 12:10:11 GMT