Definitive XML Schema

Priscilla Walmsley (pwalmsley@datypic.com)
1st edition (December 7, 2001)
Prentice Hall PTR; ISBN: 0130655678

Chapter 19: Topics for DTD users

Book Examples

<!ELEMENT price (#PCDATA)>

<xsd:element name="price" type="xsd:decimal"/>

Example 19-2. Simple content (with attributes)

<!ELEMENT price (#PCDATA)>
<!ATTLIST price currency NMTOKEN #IMPLIED>

<xsd:element name="price">
  <xsd:complexType>
    <xsd:simpleContent>
      <xsd:extension base="xsd:decimal">
        <xsd:attribute name="currency" type="xsd:NMTOKEN"/>
      </xsd:extension>
    </xsd:simpleContent>
  </xsd:complexType>
</xsd:element>

Example 19-3. Complex content

<!ELEMENT product (number, name+, size?, color*)>

<xsd:element name="product">
  <xsd:complexType>
    <xsd:sequence>
      <xsd:element ref="number"/>
      <xsd:element ref="name"  maxOccurs="unbounded"/>
      <xsd:element ref="size"  minOccurs="0"/>
      <xsd:element ref="color" minOccurs="0" maxOccurs="unbounded"/>
    </xsd:sequence>
  </xsd:complexType>
</xsd:element>

Example 19-4. Nested groups

<!ELEMENT el ((a | b)*, (c | d)?)>

<xsd:element name="el">
  <xsd:complexType>
    <xsd:sequence>
      <xsd:choice minOccurs="0" maxOccurs="unbounded">
        <xsd:element ref="a"/>
        <xsd:element ref="b"/>
      </xsd:choice>
      <xsd:choice minOccurs="0" maxOccurs="1">
        <xsd:element ref="c"/>
        <xsd:element ref="d"/>
      </xsd:choice>
    </xsd:sequence>
  </xsd:complexType>
</xsd:element>

Example 19-5. Mixed content

<!ELEMENT letter (#PCDATA | custName | prodName)*>

<xsd:element name="letter">
  <xsd:complexType mixed="true">
    <xsd:choice minOccurs="0" maxOccurs="unbounded">
      <xsd:element ref="custName"/>
      <xsd:element ref="prodName"/>
    </xsd:choice>
  </xsd:complexType>
</xsd:element>

Example 19-6. Empty content

<!ELEMENT color EMPTY>
<!ATTLIST color value NMTOKEN #IMPLIED>

<xsd:element name="color">
  <xsd:complexType>
    <!-- no content model is specified here -->
    <xsd:attribute name="value" type="xsd:NMTOKEN"/>
  </xsd:complexType>
</xsd:element>

Example 19-7. Any content

<!ELEMENT anything ANY>

<xsd:element name="anything">
  <xsd:complexType mixed="true">
    <xsd:sequence>
      <xsd:any minOccurs="0" maxOccurs="unbounded"/>
    </xsd:sequence>
  </xsd:complexType>
</xsd:element>

Example 19-8. Representing an enumerated attribute

<!ATTLIST price currency (USD | CHF) "USD">

<xsd:attribute name="currency" default="USD">
  <xsd:simpleType>
    <xsd:restriction base="xsd:token">
      <xsd:enumeration value="USD"/>
      <xsd:enumeration value="CHF"/>
    </xsd:restriction>
  </xsd:simpleType>
</xsd:attribute>

Example 19-9. Representing a notation attribute

<!ATTLIST picture fmt NOTATION (jpg | gif) "jpg">

<xsd:attribute name="fmt" default="jpg">
  <xsd:simpleType>
    <xsd:restriction base="xsd:NOTATION">
      <xsd:enumeration value="jpg"/>
      <xsd:enumeration value="gif"/>
    </xsd:restriction>
  </xsd:simpleType>
</xsd:attribute>

Example 19-10. Attribute declarations

<!ATTLIST product
    id ID #REQUIRED
    name CDATA #IMPLIED
    type NMTOKEN "PR"
    version NMTOKEN #FIXED "A123">

<xsd:attribute name="id" type="xsd:ID" use="required"/>
<xsd:attribute name="name" type="xsd:normalizedString"
               use="optional"/>
<xsd:attribute name="type" type="xsd:NMTOKEN" default="PR"/>
<xsd:attribute name="version" type="xsd:NMTOKEN" fixed="A123"/>

Example 19-11. Notation

<!NOTATION jpeg SYSTEM "JPG">

<xsd:notation name="jpeg" system="JPG"/>

Example 19-12. Reusing entire content models

<!ENTITY % AOrB "(a | b)">

<!ELEMENT x %AOrB;>
<!ELEMENT y %AOrB;>

<xsd:complexType name="AOrBType">
  <xsd:choice>
    <xsd:element ref="a"/>
    <xsd:element ref="b"/>
  </xsd:choice>
</xsd:complexType>

<xsd:element name="x" type="AOrBType"/>
<xsd:element name="y" type="AOrBType"/>

Example 19-13. Reusing fragments of content models

<!ENTITY % AOrB "a | b">

<!ELEMENT x ((%AOrB;) , c)>

<xsd:group name="AOrBGroup">
  <xsd:choice>
    <xsd:element ref="a"/>
    <xsd:element ref="b"/>
  </xsd:choice>
</xsd:group>

<xsd:element name="x">
  <xsd:complexType>
    <xsd:sequence>
      <xsd:group ref="AOrBGroup"/>
      <xsd:element ref="c"/>
    </xsd:sequence>
  </xsd:complexType>
</xsd:element>

Example 19-14. Reusing groups of attributes

<!ENTITY % HeaderGroup "id ID #REQUIRED
                variety NMTOKEN #IMPLIED">

<!ATTLIST x %HeaderGroup;>

<xsd:attributeGroup name="HeaderGroup">
  <xsd:attribute name="id" type="xsd:ID" use="required"/>
  <xsd:attribute name="variety" type="xsd:NMTOKEN"/>
</xsd:attributeGroup>

<xsd:element name="x">
  <xsd:complexType>
    <xsd:attributeGroup ref="HeaderGroup"/>
  </xsd:complexType>
</xsd:element>

Example 19-15. Allowing future extensions for sequence groups

<!ENTITY % ext "" >
<!ELEMENT x (a , b %ext;)>

<xsd:complexType name="XType">
  <xsd:sequence>
    <xsd:element ref="a"/>
    <xsd:element ref="b"/>
  </xsd:sequence>
</xsd:complexType>
<xsd:element name="x" type="XType"/>

Example 19-16. Implementing extensions for sequence groups

<!ENTITY % ext ", c, d" >
<!ENTITY % original SYSTEM "original.dtd">
%original;

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <xsd:redefine schemaLocation="original.xsd">
    <xsd:complexType name="XType">
      <xsd:complexContent>
      <xsd:extension base="XType">
        <xsd:sequence>
          <xsd:element ref="c"/>
          <xsd:element ref="d"/>
        </xsd:sequence>
        </xsd:extension>
      </xsd:complexContent>
    </xsd:complexType>
  </xsd:redefine>
</xsd:schema>

Example 19-17. Allowing future extensions for choice groups

<!ENTITY % ext "" >
<!ELEMENT x (a | b %ext;)*>

<xsd:complexType name="XType">
  <xsd:choice>
    <xsd:element ref="a"/>
    <xsd:element ref="b"/>
    <xsd:element ref="ext"/>
  </xsd:choice>
</xsd:complexType>
<xsd:element name="x" type="XType"/>
<xsd:element name="ext" abstract="true" type="xsd:string"/>

Example 19-18. Implementing extensions for choice groups

<!ENTITY % ext "| c | d" >
<!ENTITY % original SYSTEM "original.dtd">
%original;

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <xsd:include schemaLocation="original.xsd"/>
  <xsd:element name="c" substitutionGroup="ext"/>
  <xsd:element name="d" substitutionGroup="ext"/>
</xsd:schema>

Example 19-19. Allowing future extensions for attributes

<!ENTITY % attExt "" >
<!ATTLIST x id ID #REQUIRED
        %attExt;>

<xsd:complexType name="XType">
  <!-- content model here -->
  <xsd:attribute name="id" type="xsd:ID" use="required"/>
</xsd:complexType>
<xsd:element name="x" type="XType"/>

Example 19-20. Implementing extensions for attributes

<!ENTITY % attExt "myAttr NMTOKEN #IMPLIED" >
<!ENTITY % original SYSTEM "original.dtd">
%original;

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <xsd:redefine schemaLocation="original.xsd">
    <xsd:complexType name="XType">
      <xsd:complexContent>
        <xsd:extension base="XType">
          <xsd:attribute name="myAttr" type="xsd:NMTOKEN"/>
        </xsd:extension>
      </xsd:complexContent>
    </xsd:complexType>
  </xsd:redefine>
</xsd:schema>

Example 19-21. Allowing future extensions for attribute groups

<!ENTITY % attExt "" >
<!ENTITY % HeaderGroup "id ID #REQUIRED
                        variety NMTOKEN #IMPLIED
                        %attExt;">
<!ATTLIST x %HeaderGroup;>

<xsd:attributeGroup name="HeaderGroup">
  <xsd:attribute name="id" type="xsd:ID" use="required"/>
  <xsd:attribute name="variety" type="xsd:NMTOKEN"/>
</xsd:attributeGroup>

<xsd:element name="x">
  <xsd:complexType>
    <xsd:attributeGroup ref="HeaderGroup"/>
  </xsd:complexType>
</xsd:element>

Example 19-22. Implementing extensions for attribute groups

<!ENTITY % attExt "myAttr NMTOKEN #IMPLIED" >
<!ENTITY % original SYSTEM "original.dtd">
%original;

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <xsd:redefine schemaLocation="original.xsd">
    <xsd:attributeGroup name="HeaderGroup">
      <xsd:attributeGroup ref="HeaderGroup"/>
      <xsd:attribute name="myAttr" type="xsd:NMTOKEN"/>
    </xsd:attributeGroup>
  </xsd:redefine>
</xsd:schema>

Example 19-23. Including other DTDs/schema documents

<!ENTITY % prodInfo SYSTEM "prod.dtd">
%prodInfo;

<xsd:include schemaLocation="prod.xsd"/>

Example 19-24. Unparsed entity

<xsd:element name="product">
  <xsd:complexType>
    <xsd:attribute name="number" type="ProdNumType"/>
    <xsd:attribute name="picture" type="xsd:ENTITY"/>
  </xsd:complexType>
</xsd:element>

<!DOCTYPE catalog [
<!NOTATION jpeg SYSTEM "JPG">
<!ENTITY prod557 SYSTEM "prod557.jpg" NDATA jpeg>
<!ENTITY prod563 SYSTEM "prod563.jpg" NDATA jpeg>
]>

<catalog>
  <product number="557" picture="prod557"/>
  <product number="563" picture="prod563"/>
</catalog>

Example 19-25. Comments

<!-- ******************** -->
<!-- CUSTOMER INFORMATION -->
<!-- ******************** -->

<!-- billing address -->
<!ELEMENT billTo (%AddressType;)>
<!-- shipping address -->
<!ELEMENT shipTo (%AddressType;)>

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
            xmlns:doc="http://example.org/doc">

  <xsd:annotation>
    <xsd:documentation>
      <doc:section>CUSTOMER INFORMATION</doc:section>
    </xsd:documentation>
  </xsd:annotation>

  <xsd:element name="billTo" type="AddressType">
    <xsd:annotation>
      <xsd:documentation>
        <doc:description>billing address</doc:description>
      </xsd:documentation>
    </xsd:annotation>
  </xsd:element>

  <xsd:element name="shipTo" type="AddressType">
    <xsd:annotation>
      <xsd:documentation>
        <doc:description>shipping address</doc:description>
      </xsd:documentation>
    </xsd:annotation>
  </xsd:element>
</xsd:schema>