XSD error with tag types

When building code :

<types>
    <xs:schema targetNamespace="urn:sigiss_ws">
        <xs:import namespace="http://schemas.xmlsoap.org/soap/encoding/"/>
        <xs:import namespace="http://schemas.xmlsoap.org/wsdl/"/>
        <xs:complexType name="tcDescricaoRps">
        <xs:all>
            <xs:element name="ccm" type="xs:string" minOccurs="1" maxOccurs="1"/>
        </xs:all>
    </xs:schema>
</types>

I get an eclipse error message:

  

s4s-elt-invalid-content.1: The content of 'schema' is invalid.   Element 'types' is invalid, misplaced, or occurs too often.