- From: Joseph M. Reagle Jr. <reagle@w3.org>
- Date: Fri, 27 Jul 2001 18:14:35 -0400
- To: "John Boyer" <jboyer@PureEdge.com>, "Donald Eastlake" <dee3@torque.pothole.com>, <lde008@dma.isg.mot.com>
- Cc: "IETF/W3C XML-DSig WG" <w3c-ietf-xmldsig@w3.org>
Comment on : http://www.w3.org/Signature/Drafts/xml-exc-c14n
A performance requirement I'd like on exclusive canonicalization is that it
be equal to or faster than Canonical XML. Since it is seemingly doing less,
this seems like a natural result, and since it appears folks will be using
this algorithm frequently to detach a payload, efficient (single?) child
element canonicalization would be a good thing.
Presently, Canonical XML requires one to keep the state of ancestors (their
namespace declarations and whether they've already been rendered (if they
are in the subset)). Exclusive canonicalization doesn't require one to worry
about ancestor xml:foo attributes which is ok, but that ancestor context
still needs to be processed so there's little savings there. While the
"PertinentNamespaceDeclarations" is nice in that it doesn't keep namespace
declarations never used, it requires additional descendent processing to
determine if the namespace is visibly utilized. As specified in the spec,
("one method for implementing"), this is certainly more expensive. The best
implementation I've heard of would to have preprocess the whole document
(not including parsing) at least once.
Consequently, I'd like to remove processing of "the XML parse subtree rooted
by PN contains an element E that is in the document subset and visibly
utilizes N." I don't think this hinders anything and it's equivalent to
Canonical XML. I can't think of anyway to make it faster while staying
within the XPath model. (If people wanted to diverge, one could consider the
old Canonical XML [1], but that would take us back to prefix rewriting I
think...)
[1] http://www.w3.org/TR/2000/WD-xml-c14n-20000119.html
--
Joseph Reagle Jr. http://www.w3.org/People/Reagle/
W3C Policy Analyst mailto:reagle@w3.org
IETF/W3C XML-Signature Co-Chair http://www.w3.org/Signature
W3C XML Encryption Chair http://www.w3.org/Encryption/2001/
Received on Friday, 27 July 2001 18:14:45 UTC