Deriving by restriction

• You can derive new simple types types from existing types by restricting the type to a subset of its normal values

• An xsd:simpleType element defines the restricted type

• The name attribute of xsd:simpleType assigns a name to the new type.

• An xsd:restriction child element specifies what type is being restricted via its base attribute.

• Facet children of xsd:restriction specify the constraints on the type.

• For example, this xsd:simpleType element defines a phonoYear as any year from 1877 (the year Edison invented the phonograph) on:

  <xsd:simpleType name="phonoYear">
    <xsd:restriction base="xsd:gYear">
      <xsd:minInclusive value="1877"/>
    </xsd:restriction>
  </xsd:simpleType>
   

• Then you declare the year element like this:

  <xsd:element type="phonoYear" />