Hi, Beside the former error report of query Xen_HostSystem from Xen_VirtualSystemManagementCapabilities according to Xen_ElementCapabilities association, that is to say, with a non exist VirtualSystemManagementCapabilities, we can still get excepted result as following. wbemcli ain -ac Xen_ElementCapabilities http://root:password@localhost/root/virt:Xen_VirtualSystemManagementCapabili..." wrong" localhost:5988/root/virt:Xen_HostSystem.CreationClassName="Xen_HostSystem",Name="wks230838wss.cn.ibm.com" Meanwhile, other associations have the same problems. With a non exist ComputerSystem instance, we can still get expected association. wbemcli ain -ac Xen_ElementCapabilities http://root:password@localhost/root/virt:Xen_ComputerSystem.CreationClassName="Xen_ComputerSystem",Name=" wrong" localhost:5988/root/virt:Xen_EnabledLogicalElementCapabilities.InstanceID="wrong" However, there is no error report when I do invalid reverse query of Xen_EnabledLogicalElementCapabilities. wbemcli ain -ac Xen_ElementCapabilities http://root:password@localhost/root/virt:Xen_EnabledLogicalElementCapabiliti..." wrong" As we know, Xen_AllocationCapabilities associate with ResourcePool by Xen_ElementCapabilities. There are still errors from two sides querying. wbemcli ain -ac Xen_ElementCapabilities http://root:password@localhost/root/virt:Xen_AllocationCapabilities.InstanceID="ProcessorPool/0" * * wbemcli: Cim: (7) CIM_ERR_NOT_SUPPORTED: The requested operation is not supported * wbemcli ain -ac Xen_ElementCapabilities http://root:password@localhost/root/virt:Xen_MemoryPool.InstanceID="wrong" localhost:5988/root/virt:Xen_AllocationCapabilities.InstanceID="wrong" Please who can have a look into them? Thanks! Best, Regards Daisy Guo Lian Yun E-mail: yunguol@cn.ibm.com IBM China Development Lab, Shanghai, China TEL: (86)-21-61008057