With a non existing instance, e.g. a wrong key name or value, Xen_VirtualSystemManagementCapabilities still return expected results below: wbemcli ain -ac Xen_ElementCapabilities http://root:password@localhost/root/virt:Xen_VirtualSystemManagementCapab... wrong" localhost:5988/root/virt:Xen_HostSystem.CreationClassName="Xen_HostSystem",Name="zeit" wbemcli ain -ac Xen_ElementCapabilities http://root:password@localhost/root/virt:Xen_VirtualSystemManagementCapab.... Wrong="wrong" localhost:5988/root/virt:Xen_HostSystem.CreationClassName="Xen_HostSystem",Name="zeit" The same problem with Xen_VirtualSystemMigrationCapabilities. In conclusion, four association providers have the same problems, that is still return expected result with non existing instance from one or two sides querying. They are Xen_HostedResourcePool, Xen_ResourceAllocationFromPool, Xen_HostedService and Xen_ElementCapabilities. Please who can have a look into them? Thanks a lot! Best, Regards Daisy Guo Lian Yun E-mail: yunguol(a)cn.ibm.com IBM China Development Lab, Shanghai, China TEL: (86)-21-61008057