W3C home > Mailing lists > Public > www-xml-schema-comments@w3.org > April to June 2000

[Joey Coyle <joey@xcoyle.com>] restriction

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 26 May 2000 09:01:06 +0100
To: www-xml-schema-comments@w3.org
Message-ID: <f5bn1ldd9kt.fsf@cogsci.ed.ac.uk>



attached mail follows:


There are many in the ASN.1 world that want to move to XML Schema, and if I 
am reading correctly, it seems you have said no to many.

When modeling by restriction, which is quite common, you have jumbled the 
meaning of minOccurs.  It means both that instances must contain data for 
that element, and secondly that derived types by restriction must include 
that element.

This is not logical.  There are many circumstances when you want an 
elemental data slot filled in a parent type instance, and then don't even 
want the element in a derived child.

##################################################

The next issue I would like to address is about the level of 
restriction.  Can you explain this:

A complex type with an empty specification for {final} can be used as a 
{base type definition} for other types derived by either of extension or 
restriction; the explicit values extension, and restriction prevent further 
derivations by extension and restriction respectively. If all values are 
specified, then the complex type is said to be [Definition:]  final: no 
further derivations are possible.

Does it mean that a type which is derived by restriction and is 
instantiable, can not be used as a base type for further restriction?

thank you,
Joseph Coyle MD, PhD Candidate




-- 
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2001, part-time member of W3C Team
     2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
	    Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
		     URL: http://www.ltg.ed.ac.uk/~ht/
Received on Friday, 26 May 2000 04:01:14 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 23:08:47 UTC