XML Tutorial/XML Schema/choice

Allow the document instance author to use the initial element twice

   <source lang="xml">

<xsd:element name="middleName">

 <xsd:complexType>
  <xsd:choice>
   <xsd:element name="initial" type="xsd:string" maxOccurs="2"/>
   <xsd:element name="name" type="xsd:string"/>
  </xsd:choice>
 </xsd:complexType>

</xsd:element></source>

<choice> Declarations

   <source lang="xml">

<choice minOccurs="non negative number"

       maxOccurs="non negative number or unbounded"> 

You can specify multiple child declarations within a <choice> declaration. In an instance document, only one of the declarations may be used. <choice>

   <element name="first" type="string" minOccurs="1" maxOccurs="unbounded"/> 
   <element name="middle" type="string" minOccurs="0" maxOccurs="1"/> 
   <element name="last" type="string"/> 

</choice> <choice> declaration may contain <element> declarations, element wild-cards, and inner <sequence>, <choice>, or <group>references.</source>

Creating a Set of Choices

   <source lang="xml">

With the default minOccurs and maxOccurs attribute values (both equal to 1), only one of the elements in a set of choices can appear. If the value of the maxOccurs attribute is greater than 1, that value determines how many of the choices may appear. A set of choices can also contain nested sequences, additional choice sets, or references to named groups. A set of choices may be contained in a complex type definition, in sequences, in other sets of choices, or in named group definitions.

File: Schema.xsd <?xml version="1.0"?> <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"

 targetNamespace="http://www.wbex.ru" xmlns="http://www.wbex.ru"
 elementFormDefault="qualified">
   <xsd:element name="animal" type="animalType" />
 <xsd:complexType name="animalType">
   <xsd:choice>
     <xsd:element name="subspecies" type="xsd:string" />
     <xsd:sequence>
       <xsd:element name="region" type="xsd:string" />
       <xsd:element name="population" type="xsd:integer" />
     </xsd:sequence>
   </xsd:choice>
 </xsd:complexType>

</xsd:schema>

File: Data.xml <?xml version="1.0"?> <animal xmlns="http://www.wbex.ru">

 <subspecies>Russia</subspecies>

</animal></source>

You can further express occurrence behavior by using the minOccurs and maxOccurs attributes with either the choice element or the element declarations themselves.

   <source lang="xml">

<xsd:element name="middleName">

 <xsd:complexType>
  <xsd:choice maxOccurs="2">
   <xsd:element name="initial" type="xsd:string"/>
   <xsd:element name="name" type="xsd:string"/>
  </xsd:choice>
 </xsd:complexType>

</xsd:element> The middleName element to contain one of two child elements: initial or name <middleName>

 <initial>S</initial>

</middleName> <middleName>

 <name>Stolte</name>

</middleName> To allow for this content model, we would have to use the choice element: <xsd:element name="middleName">

 <xsd:complexType>
  <xsd:choice>
   <xsd:element name="initial" type="xsd:string"/>
   <xsd:element name="name" type="xsd:string"/>
  </xsd:choice>
 </xsd:complexType>

</xsd:element></source>