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Re: final on element declaration

From: Jeni Tennison <jeni@jenitennison.com>
Date: Sat, 27 Apr 2002 10:36:01 +0100
Message-ID: <186434724430.20020427103601@jenitennison.com>
To: "Don Smith" <donalds@isogen.com>
CC: "Schema" <xmlschema-dev@w3.org>
Hi Don,

> What is the purpose of the "final" attribute on an element
> declaration?
> I understand its use on a type definition, but can't figure out what
> it means to prohibit a derivation from a declaration.

An element declaration is "derived" from another when its part of the
*substitution group* of that element declaration. Controls like final,
abstract and (partially) block determine whether an element can or
can't be (or has to be) the head of a substitution group.

Setting final to true means that it can't be cited as the head element
of a substitution group; setting abstract to true means that the
element itself can't be used in the instance, but has to be
substituted by some other element.



Jeni Tennison
Received on Saturday, 27 April 2002 05:36:03 UTC

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