schema.xsd

<element name="KeyInfo" type="ds:KeyInfoType"/> 
   <complexType name="KeyInfoType" mixed="true">
     <choice maxOccurs="unbounded">     
       <element ref="ds:KeyName"/> 
       <element ref="ds:KeyValue"/> 
       <element ref="ds:RetrievalMethod"/> 
       <element ref="ds:X509Data"/> 
       <element ref="ds:PGPData"/> 
       <element ref="ds:SPKIData"/>
       <element ref="ds:MgmtData"/>
       <any processContents="lax" namespace="##other"/>
       <!-- (1,1) elements from (0,unbounded) namespaces -->
     </choice>
     <attribute name="Id" type="ID" use="optional"/>
   </complexType>
</element>