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Re: final=""

From: Stanley Guan <stanley.guan@oracle.com>
Date: Wed, 27 Feb 2002 10:26:53 -0800
Message-ID: <3C7D24ED.C6575D81@oracle.com>
CC: Schema XML <xmlschema-dev@w3.org>
Henry,

Thank you for your answers.  So similar interpretation applied
to other attributes:
   finalDefault,
   blockDefault,
   final, and
   block!

-Stanley


"Henry S. Thompson" wrote:

> Stanley Guan <stanley.guan@oracle.com> writes:
>
> > Hi,
> >
> > Is empty string an allowed value for attribute "final" as shown
> > below?
> >
> >  <xsd:element name="fe_valid" final="" type="tns:sd"/>
> >
> > XSV seems to take it o.k.  But, as shown in the spec.:
> >   <element
> >     (snip)
> >     final = (#all | List of (extension | restriction))
> >     (snip)
> >   </element>
> >
> > Does this mean the only acceptable values for attribute
> > "final" are:
> >   "#all",
> >   "extension", or
> >   "restriction"?
>
> The tableaux are non-normative, but are derived from the sForS, which
> is the normative reference here:
>
>   <xs:union>
>    <xs:simpleType>
>     <xs:restriction base="xs:token">
>      <xs:enumeration value="#all"/>
>     </xs:restriction>
>    </xs:simpleType>
>    <xs:simpleType>
>     <xs:list itemType="xs:reducedDerivationControl"/>
>    </xs:simpleType>
>   </xs:union>
>
>  <xs:simpleType name="reducedDerivationControl">
>   <xs:restriction base="xs:derivationControl">
>    <xs:enumeration value="extension"/>
>    <xs:enumeration value="restriction"/>
>   </xs:restriction>
>  </xs:simpleType>
>
> So in fact all the following are allowed:
>
> final="#all"        (first branch of the union)
> final=""            (2nd branch of the union, length 0)
> final="extension"   (2nd branch of the union, length 1)
> final="restriction" (2nd branch of the union, length 1)
> final="extension restriction"   (2nd branch of the union, length 2)
>
> and a bunch of useless variations are also allowed
>
> final="restriction extension" (2nd branch of the union, length 2)
> final="restriction restriction" (2nd branch of the union, length 2)
> final="extension extension" (2nd branch of the union, length 2)
> final="restriction extension restriction" (2nd branch of the union, length 3)
>
> We could/probably should have restricted the length to two, but that
> still would have left some redundancy.  Doesn't matter to the
> semantics.
>
> If you read the relevant mapping prose for {substitution group
> exclusions} in 3.3.2 [1] you will see that the length 0 list is
> entirely reasonable, is in fact the default (via the 'finalDefault'
> attribute on <xs:schema>), and means that the element's use as a
> substitution group head is not constrained.
>
> ht
>
> [1] http://www.w3.org/TR/xmlschema-1/#declare-element
> --
>   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 Wednesday, 27 February 2002 13:27:09 GMT

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