XML Schema Complete Reference, The

6.10. Substitution Groups

A substitution group consists of a set of element types. An element type associates itself with a substitution group by specifying a substitutionGroup attribute. The value of that attribute indicates that the new element type is a valid substitution for the referenced element type. The substitutions occur in complex type derivations or in an XML instance. Listing 6.7 is the sequenceID substitution group.

Listing 6.7. A Substitution Group

<xsd:element name="sequenceID" type="sequenceIDType" abstract="true"> <xsd:annotation> <xsd:documentation xml:lang="en"> This element type is non-instantiable: the element must be replaced by a substitution group in either a derived type or an instance. </xsd:documentation> </xsd:annotation> ...