This figure has a main label "XML schema, emp. xsd". It shows two columns of XML elements. Two elements are shown in each column, with ellipses ("...") after each column element. There is an arrow from the lower element shown in each column to the upper element shown in the other column. The upper element shown in the left column is <xs:complexType name="CT1"...>. The lower is <xs:element name="e2" type="CT2"/>. The upper element shown in the right column is <xs:complexType name="CT2"...>. The lower is <xs:element name="e2" type="CT1"/>.