Re: Clarification of expected behaviour in the presence of schema validation information

Hi John,
I'm not an authority on XML Dsig but if the schema's base64 type implies
(as you write) that white space is collapsed the problem seems to be that the
generator doesn't honor the declaration.

Regarding schema validation and XML Dsig there are numerous of problems
most notably attribute defaults that essentially are useless in signed data,
unless the signature generator is also required to interpret the schema which
I believe is fairly little supported in existing APIs.

>From a practical point-of-view I would recommend to avoid constructs
that depend on schema-aware signature validation, but ban generators
that doesn't follow the schema.

Cheers,
Anders Rundgren


----- Original Message ----- 
From: "John Keeping" <john@metanate.com>
To: <w3c-ietf-xmldsig@w3.org>
Sent: Friday, June 12, 2009 19:57
Subject: Clarification of expected behaviour in the presence of schema validation information


Hi,

We've recently implemented XML digital signature support for an XML
format with an associated schema which defines an element as type
xs:base64Binary. This implies that white space in the element's content
is to be collapsed.

Indeed, when reading in the XML file, Xerces-C generates a DOM tree in
which new lines in the content have been collapsed to single spaces.
However the digest has been calculated over text content containing the
new lines.

Given that both applications have the schema available to them, what
would you expect the behaviour to be in this case?

As far as I can see there are three possibilities:

1. The generating application collapses white space in its output in
order to be compatible with both a receiving application which has the
schema and one which does not

2. The receiving application ignores the white space directive from the
schema

3. The generating application adds an explicit xml:space="collapse"
attribute to the element


Thanks,

John

-- 
John Keeping
Metanate Ltd
www.metanate.com (Software consultancy)
www.schemus.com (Data synchronisation)

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Received on Saturday, 13 June 2009 08:12:57 UTC