This compositor defines the occurrence of elements in the predefined order.
<xs:element name="ElementName"> <xs:complexType> <xs:sequence> .../... </xs:sequence> .../... </xs:complexType> </xs:element>
Sequence is a content model that allows occurrence of the defined sequence of child elements.
(xs prefix is bound to NS with the URL http://www.w3.org/2001/XMLSchema(
Either <xs:choice> or <xs:all> can be used instead of<xs:sequence>.