W3C home > Mailing lists > Public > xml-encryption@w3.org > November 2001

Re: Deep Extension

From: Joseph Reagle <reagle@w3.org>
Date: Thu, 29 Nov 2001 13:56:42 -0500
To: Jeni Tennison <jeni@jenitennison.com>
Cc: xmlschema-dev@w3.org, henry@w3.org, xenc <xml-encryption@w3.org>
Message-Id: <20011129185643.6DB21B6@policy.w3.org>
On Thursday 29 November 2001 06:03, Jeni Tennison wrote:
> When you extend a type, the start of the content model of the new type
> has to be exactly the same as the start of the base type. That means
> you can't change the type of an element from the base type when you
> derive by extension.

Hi Jenni,

Thank you for your thoughtful email, your solutions describe what I thought 
(feared) was the order of magnitude necessary to meet the requirement. 
We are trying to use schema in two ways. First, to provide a 
complete/precise definition that a schema validator can use to check 
instance syntax. Second, to communicate via excerpts in the specification 
the data structure and processing required of implementations. We can get 
"complex" with multiple derived types which is fine for the machine, but 
doesn't really help readers of the spec: creating a whole intermediary type 
just to restrict-then-expand, or create a type just to remove the nonce 
would make the spec more confusing...

Consequently, I'm thinking Takeshi's solution might be the least awkward of 
the options available to us, "I agree with you that it is not so easy to 
remove the Nonce attribute from the CipherData element.  So how about 
containing the attribute not in the [CipherData] element but in the 
EncryptedData element, though it may be a little weird..."


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 Thursday, 29 November 2001 13:56:53 UTC

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