RE: Use of Substitution Groups

Take 2.1.

Another scenario is that a type author wishes any extensions to conform
to certain constraints.  In our Name example, the author wishes to
ensure that an xml:lang attribute is always present.  Wildcards do not
permit this kind of constraint.  Instead, the author uses substitution
groups.  This style can be considered use of substitution groups "at the
bottom" because the substitution group is on each of the contents of the
type.  Family, given then middle are of the same type
(namens:personNameContentType).  Only PersonNameContent elements are
allowed as extensions, and it is abstract and constrained to be of type
namens:personNameContentType.  PersonNameContentType has a constraint
that xml:lang is required.

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:namens="http://www.example.org/name/1"
targetNamespace="http://www.example.org/name/1">
  <xs:import namespace="http://www.w3.org/XML/1998/namespace"
schemaLocation="http://www.w3.org/2001/xml.xsd"/>
  <xs:element name="personName" type="namens:nameType"/>
  <xs:complexType name="nameType">
    <xs:sequence>
      <xs:element ref="namens:family"/>
      <xs:element ref="namens:given"/>
      <xs:element ref="namens:PersonNameContent" minOccurs="0"
maxOccurs="unbounded"/>
    </xs:sequence>
    <xs:anyAttribute namespace="##any" processContents="strict"/>
  </xs:complexType>
  <xs:element name="PersonNameContent"
type="namens:PersonNameContentType" abstract="true"/>
  <xs:element name="given" type="namens:PersonNameContentType"/>
  <xs:element name="family" type="namens:PersonNameContentType"/>
  <xs:complexType name="PersonNameContentType">
    <xs:simpleContent>
      <xs:extension base="xs:string">
        <xs:attribute ref="xml:lang" use="required"/>
        <xs:anyAttribute namespace="##any" processContents="strict"/>
      </xs:extension>
    </xs:simpleContent>
  </xs:complexType>
  <xs:element name="personNameWithMiddle"
type="namens:nameWithMiddleType"/>
  <xs:complexType name="nameWithMiddleType">
    <xs:sequence>
      <xs:element ref="namens:given"/>
      <xs:element ref="namens:family"/>
      <xs:element ref="namens:middle" minOccurs="0"/>
      <xs:element ref="namens:PersonNameContent" minOccurs="0"
maxOccurs="unbounded"/>
    </xs:sequence>
    <xs:anyAttribute namespace="##any" processContents="strict"/>
  </xs:complexType>
  <xs:element name="middle" type="namens:PersonNameContentType"/>
</xs:schema>

As with the use of extension or restriction, the consumer must know
about the new type when processing personNameWithMiddle elements.  As
with wildcards, the producer could use the personName elements to
contain middle elements by identifying the middle element with
xsi:type="namens:PersonNameContentType".  This gives the producer of
middle elements the option of either reusing the personName (and using
xsi:type) or using the new personNameWithMiddle element.  The
personNameWithMiddle could also have been constructed using
xsd:restriction rather than complete respecification.

Cheers,
Dave 

> -----Original Message-----
> From: www-tag-request@w3.org [mailto:www-tag-request@w3.org] 
> On Behalf Of David Orchard
> Sent: Wednesday, May 02, 2007 2:43 PM
> To: www-tag@w3.org
> Subject: RE: Use of Substitution Groups
> 
> 
> Take 2.  
> 
> Is this right?
> 
> Another scenario is that a type author wishes any extensions 
> to conform to certain constraints.  In our Name example, the 
> author wishes to ensure that an xml:lang attribute is always 
> present.  Wildcards do not permit this kind of constraint.  
> Instead, the author uses substitution groups.  This style can 
> be considered use of substitution groups "at the bottom" 
> because the substitution group is on each of the contents of 
> the type.  Family, given then middle are of the same type 
> (namens:personNameContentType).  Only PersonNameContent 
> elements are allowed as extensions, and it is abstract and 
> constrained to be of type namens:personNameContentType.  
> PersonNameContentType has a constraint that xml:lang is required.
> 
> <?xml version="1.0" encoding="UTF-8"?>
> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
> xmlns:namens="http://www.example.org/name/1"
> targetNamespace="http://www.example.org/name/1">
> <xs:import namespace="http://www.w3.org/XML/1998/namespace"
> schemaLocation="http://www.w3.org/2001/xml.xsd"/>
> 
> 	<xs:element name="personName" type="namens:nameType" />
> 	<xs:complexType name="nameType">
> 		<xs:sequence minOccurs="0" maxOccurs="unbounded">
> 			<xs:choice>
> 				<xs:element
> ref="namens:PersonNameContent" minOccurs="0"/>
> 				<xs:element ref="namens:family"
> minOccurs="1"/>
> 				<xs:element ref="namens:given"
> minOccurs="1"/>
> 			</xs:choice>
> 		</xs:sequence>
> 		<xs:anyAttribute namespace="##any"
> processContents="strict"/>
> 	</xs:complexType>
> 	
> 	<xs:element name="PersonNameContent" abstract="true"
> type="namens:PersonNameContentType"/>
> 	<xs:element name="given" type="namens:PersonNameContentType"/>
> 	<xs:element name="family" type="namens:PersonNameContentType"/>
> 
> 	<xs:complexType name="PersonNameContentType">
> 	    <xs:simpleContent>
> 		  <xs:extension base="xs:string">
> 			<xs:attribute ref="xml:lang"  use="required"/>
> 		 	<xs:anyAttribute namespace="##any"
> processContents="strict"/>
> 		  </xs:extension>
> 		</xs:simpleContent>
> 	</xs:complexType>
> 	
> 	<xs:element name="personNameWithMiddle"
> type="namens:nameWithMiddleType"/>
> 	<xs:complexType name="nameWithMiddleType">
> 		<xs:sequence minOccurs="0" maxOccurs="unbounded">
> 			<xs:choice>
> 				<xs:element
> ref="namens:PersonNameContent" minOccurs="0"/>
> 				<xs:element ref="namens:given"
> minOccurs="1"/>
> 				<xs:element ref="namens:family"
> minOccurs="1"/>
> 				<xs:element ref="namens:middle"
> minOccurs="0"/>
> 			</xs:choice>
> 		</xs:sequence>
> 		<xs:anyAttribute namespace="##any"
> processContents="strict"/>
> 	</xs:complexType>
> 
> 	<xs:element name="middle" type="namens:PersonNameContentType"/>
> 	
> </xs:schema>
> 
> As with the use of extension, the consumer must know about 
> the new type when processing personNameWithMiddle elements.  
> As with wildcards, the producer could use the personName 
> elements to contain middle elements by identifying the middle 
> element with xsi:type="namens:PersonNameContentType".  This 
> gives the producer of middle elements the option of either 
> reusing the personName (and using
> xsi:type) or using the new personNameWithMiddle element.
> 
> Cheers,
> Dave 
> 
> > -----Original Message-----
> > From: www-tag-request@w3.org 
> [mailto:www-tag-request@w3.org] On Behalf 
> > Of David Orchard
> > Sent: Monday, April 23, 2007 12:57 PM
> > To: www-tag@w3.org
> > Subject: Use of Substitution Groups
> > 
> > 
> > Henry, Dan, etc.,
> > 
> > Is this the scenario that you are talking about?
> > 
> > personName and personNameWithMiddle are of 2 different 
> types that are 
> > in the substitution group for AbstractPersonName.
> > It's more interesting when the personNameWithMiddle is in a 
> different 
> > schema doc and namespace, but this is the heart of it.
> > 
> > <?xml version="1.0" encoding="UTF-8"?> <xs:schema 
> > xmlns:xs="http://www.w3.org/2001/XMLSchema"
> >       targetNamespace="http://www.example.org/name/1" 
> >       xmlns:namens="http://www.example.org/name/1">
> > 
> >  <xs:element name="AbstractPersonName" abstract="true"/> 
> <xs:element 
> > name="personName" type="namens:nameType"
> > substitutionGroup="namens:AbstractPersonName"/>
> >   
> >  <xs:complexType name="nameType">
> > 	 <xs:sequence minOccurs="0" maxOccurs="unbounded">
> > 		 <xs:choice>
> > 			 <xs:element ref="namens:given" /> 
> > 			 <xs:element ref="namens:family" /> 
> > 		  </xs:choice>
> > 	  </xs:sequence>
> > 	  <xs:anyAttribute namespace="##any" processContents="strict" />
> > 
> >   </xs:complexType>
> >   
> >   <xs:element name="given" type="xs:string"/>
> >   <xs:element name="family" type="xs:string"/>
> >   
> >  <xs:complexType name="nameWithMiddleType">
> > 	 <xs:sequence minOccurs="0" maxOccurs="unbounded">
> > 		 <xs:choice>
> > 		   <xs:element ref="namens:given" /> 
> > 		   <xs:element ref="namens:family" /> 
> > 		   <xs:element ref="namens:middle" minOccurs="0"/>
> > 		 </xs:choice>
> > 	 </xs:sequence>
> >      <xs:anyAttribute namespace="##any" processContents="strict" />
> >   </xs:complexType>
> >   
> >   <xs:element name="middle" type="xs:string"/>
> >   <xs:element name="personNameWithMiddle"
> > type="namens:nameWithMiddleType"
> > substitutionGroup="namens:AbstractPersonName"/>
> >   
> > </xs:schema>
> > 
> > Cheers,
> > Dave
> > 
> > 
> 
>

Received on Thursday, 3 May 2007 18:20:48 UTC