How to define global in XSD

I would like to define TEST as global in XSD

          <xs:element name="TEST">
            <xs:complexType>
              <xs:sequence>
                <xs:element name="TEST_LOGIN" type="xs:string" />
                <xs:element name="DOCUMENT" type="xs:string" />
              </xs:sequence>
            </xs:complexType>
          </xs:element>