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Re: XML Schemas and the Enumeration Facet

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 11 Mar 2000 09:53:12 +0000
To: www-xml-schema-comments@w3.org
Message-ID: <f5bvh2thlyv.fsf@cogsci.ed.ac.uk>
Johannes Schmidt <js99@pacbell.net> writes:

> my interpretation is that all facets are constraints, and all constraints
> must be satisfied.  for example, if you have a pattern like [A-Z]+ and a
> maxLength of 5, it means the string must both be an upper-case letter AND
> have a length of at least one (the + in the pattern) AND have a length of at
> most 5.
> 
> derived definitions add additional restrictions.  thus if you have a base
> with a maxLength of 5 and a derived type with a maxLength of 2, the derived
> type has a maximum length of 2.  similarly, if the base maxLength is 2 and
> the derived maxLength is 5, this still means the derived type has a maximum
> length of 2.  basically, the derived definition is "by restriction" which
> means a derived type can not include any values not allowed by the base
> type.
> 
> enumerations are only slightly different because if you have no
> enumerations, it means you are not limiting values by list.  if you have one
> or more enumerations, you are limiting the values by the list.  if you have
> no enumerations, you are not limiting them by a list.  here is an example:
> 
> <simpleType name="a" base="integer">
> 	<enumeration value="1"/>
> 	<enumeration value="2"/>
> 	<enumeration value="3"/>
> </simpleType>
> <simpleType name="b" base="a">
> 	<enumeration value="2"/>
> 	<enumeration value="3"/>
> 	<enumeration value="4"/>
> </simpleType>
> <simpleType name="c" base="a">
> </simpleType>
> 
> i think all of these should be legal, and a and c both have values 1,2,3
> while b has values 2,3 only.

The datatypes editor may wish to comment.  I think all your
observations are correct, and my only uncertainty is whether type "b"
is allowed.  If it _is_ allowed, its members are certainly {2,3}, as
you say.

ht
-- 
  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 Saturday, 11 March 2000 05:47:59 GMT

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