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Valid XML and Schema Normative?

From: Joseph M. Reagle Jr. <reagle@w3.org>
Date: Wed, 05 Jul 2000 16:12:56 -0400
Message-Id: <3.0.5.32.20000705161256.01a0e4a0@localhost>
To: "IETF/W3C XML-DSig WG" <w3c-ietf-xmldsig@w3.org>
I've been trying to figure out if we could go to REC prior to the Schema
specification reaching REC. To that end, one runs into the question of
whether there is a normative reference dependency? This also relates to the
following point in the STATUS:

  3. Ensure that if the syntax constraints of section 7.1 are followed, a 
  validating parser is not needed. 
  http://www.w3.org/TR/2000/WD-xmldsig-core-20000601/

A few more philosophical questions include:

1. Must you implement schema in order to implement Signature?

Generally, no.

2. If schema dramatically changed, would that change signature
processing/results?

Generally, no, the Signature Syntax would be the same.

3. If there's an error in the schema specification, would that change
signature processing/results?

Generally, no, but perhaps ..

However, the concrete question I want to ask this WG is are we using schema
merely in a descriptive capacity, or do we expect the content models to be
checked and instances validated? We aren't using that many schema features
(nor do we use the ones we employ very restrictively...) HOWEVER our present
schema precludes one from including content that we haven't specified in
SignedInfo (as does the DTD).

Consequently, if a Signature application encountered a Signature with
external content (even if namespace qualified) in SignedInfo, that Signature
should be invalid. It would only know it is invalid if it had the
DTD/Schema, consequently, a schema validating parser is REQUIRED. Right?



_________________________________________________________
Joseph Reagle Jr.   
W3C Policy Analyst                mailto:reagle@w3.org
IETF/W3C XML-Signature Co-Chair   http://www.w3.org/People/Reagle/
Received on Wednesday, 5 July 2000 16:13:56 GMT

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