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Indicators control the way how elements are to be organized in an XML document. There are seven types of indicators, falling into three broad categories.

Order Indicators

• All − Child elements can occur in any order.
• Choice − Only one of the child element can occur.
• Sequence − Child element can occur only in specified order.

Occurence Indicators

• maxOccurs − Child element can occur only maxOccurs number of times.
• minOccurs − Child element must occur minOccurs number of times.

Group Indicators

• Group − Defines related set of elements.
• attributeGroup − Defines related set of attributes.

Order Indicators

Using <all> a student element can have firstname, lastname, nickname, and marks child element in any order in the XML document.

<xs:complexType name = "StudentType" mixed = "true">
   <xs:all>
      <xs:element name = "firstname" type = "xs:string"/>
      <xs:element name = "lastname" type = "xs:string"/>
      <xs:element name = "nickname" type = "xs:string"/>
      <xs:element name = "marks" type = "xs:positiveInteger"/>
   </xs:all>
   <xs:attribute name = 'rollno' type = 'xs:positiveInteger'/>
</xs:complexType>

<xs:element name = 'student' type = 'StudentType' />

Using <choice> a student element can have only one of firstname, lastname, nickname and marks child element in the XML document.

<xs:complexType name = "StudentType" mixed = "true">
   <xs:choice>
      <xs:element name = "firstname" type = "xs:string"/>
      <xs:element name = "lastname" type = "xs:string"/>
      <xs:element name = "nickname" type = "xs:string"/>
      <xs:element name = "marks" type = "xs:positiveInteger"/>
   </xs:choice>
   <xs:attribute name = 'rollno' type = 'xs:positiveInteger'/>
</xs:complexType>

<xs:element name = 'student' type = 'StudentType' />

Using <sequence>, a student element can have firstname, lastname, nickname and marks child element in the specified order only in the XML document.

<xs:complexType name = "StudentType" mixed = "true">
   <xs:sequence>
      <xs:element name = "firstname" type = "xs:string"/>
      <xs:element name = "lastname" type = "xs:string"/>
      <xs:element name = "nickname" type = "xs:string"/>
      <xs:element name = "marks" type = "xs:positiveInteger"/>
   </xs:sequence>
   <xs:attribute name = 'rollno' type = 'xs:positiveInteger'/>
</xs:complexType>

<xs:element name = 'student' type = 'StudentType' />

Occurence Indicators

Using <maxOccurs>, a student element can have maximum two nicknames in the XML document.

<xs:complexType name = "StudentType" mixed = "true">
   <xs:all>
      <xs:element name = "firstname" type = "xs:string"/>
      <xs:element name = "lastname" type = "xs:string"/>
      <xs:element name = "nickname" type = "xs:string" maxOccurs="2"/>
      <xs:element name = "marks" type = "xs:positiveInteger"/>
   </xs:all>
   <xs:attribute name = 'rollno' type = 'xs:positiveInteger'/>
</xs:complexType>

<xs:element name = 'student' type = 'StudentType' />

Using <minOccurs>, a student element should have two nicknames in the XML document.

<xs:complexType name = "StudentType" mixed = "true">
   <xs:all>
      <xs:element name = "firstname" type = "xs:string"/>
      <xs:element name = "lastname" type = "xs:string"/>
      <xs:element name = "nickname" type = "xs:string" minOccurs="2"/>
      <xs:element name = "marks" type = "xs:positiveInteger"/>
   </xs:all>
   <xs:attribute name = 'rollno' type = 'xs:positiveInteger'/>
</xs:complexType>

<xs:element name = 'student' type = 'StudentType' />

Group Indicators

<group> is used to group a related set of elements. Here we’ve created a group of part of name and then used this group to define a student element.

<xs:group name = "infogroup">
   <xs:sequence>
      <xs:element name = "firstname" type = "xs:string"/>
      <xs:element name = "lastname" type = "xs:string"/>
      <xs:element name = "birthdate" type = "xs:date"/>
   </xs:sequence>
</xs:group>

<xs:element name = "student" type = "studentType"/>

<xs:complexType name = "studentType">
   <xs:sequence>
      <xs:group ref = "infogroup"/>
      <xs:element name = "marks" type = "xs:integer"/>
   </xs:sequence>
</xs:complexType>

<attributeGroup> is used to group a related set of attribute. Here we’ve created a group of part of name and then used this group to define attributes for student element.

<xs:attributeGroup name = "infogroup">
   <xs:sequence>
      <xs:attribute name = "firstname" type = "xs:string"/>
      <xs:attribute name = "lastname" type = "xs:string"/>
      <xs:attribute name = "birthdate" type = "xs:date"/>
   </xs:sequence>
</xs:attributeGroup>

<xs:element name = "student" type = "studentType"/>

<xs:complexType name = "studentType">
   <xs:sequence>
      <xs:attributeGroup ref = "infogroup"/>
      <xs:element name = "marks" type = "xs:integer"/>
   </xs:sequence>
</xs:complexType>