The UDDI key of an user can be obtained by executing the xquery below, likewise for a service "cs:user" should be replaced by "cs:service" and service name should be provided.
declare namespace cs = "http://namespaces.CentraSite.com/Schema/jaxr"
for $ro in collection("CentraSite")/cs:user
The UDDI key of an asset in BusinessUI can be obtained from the browsers URL. Click on the asset for which you need to get the UDDI key and then you can take it from the browser URL. (Please refer the screenshot)