Description

The restriction of a complex content complex type is an operation that allows the addition of new constraints to both the attributes and child elements in complex content elements (this reduces the set of valid instances structures). It can be seen as a declaration of intention that a new content model is a subset of a base content model (the declaration by intention is checked by the schema processors). The new content model is entirely described under xs:restriction and must represent a restriction to what was allowed by the base content model (i.e., any content valid per the restricted type must also be valid per the base type). The only exception is attributes whose description may be skipped under xs:restriction, if not changed.

Restrictions

To facilitate the checking done by schema processors, the new derived content model must follow the definition of the base type particle per particle. Each of them must be explicit derivations by restriction.

The same element name (xs:restriction) is used in three different contexts with highly different meanings. Be careful to be able to distinguish restrictions in the context of a simple datatype, a simple content model, and a complex content model.

Example

<xs:element name="author">
  <xs:complexType>
    <xs:complexContent>
      <xs:restriction base="person">
        <xs:sequence>
          <xs:element ref="name"/>
          <xs:element ref="born"/>
          <xs:element ref="dead" minOccurs="0"/>
        </xs:sequence>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>
</xs:element>

Attributes