XML Schema is an XML-based replacement for DTDs.

XML Schema describes the structure of an XML document.

The XML Schema language can also be referenced as XSD (XML Schema Definition).

XSD composite element syntax

Composite elements contain other elements and/or attributes.

XSD composite element example

<xs:element name="employee">
  <xs:complexType>
    <xs:sequence>
      <xs:element name="firstname" type="xs:string"/>
      <xs:element name="lastname" type="xs:string"/>
    </xs:sequence>
  </xs:complexType>
</xs:element>