Create common WSDL documents, 2: Custom definitions
As discussed previously, the PerformanceMonitoring and WebServer capabilities are generic and can be used by both the Java application server resources and the database server resources. WSDLs are made for both, named PerformanceMonitoringCapability.wsdl and WebServerCapability.wsdl, respectively.
It is interesting to note that in both WSDLs, standard WSDM properties are included in the WSRP document. Why not extract the WSDM properties into their own WSDL files since WSDM is generic to all manageable resources? Because you only want to use WSDM in two instances -- WSDM Metrics for PerformanceMonitoring and basic WSDM Identity for WebServer. Further abstraction is not beneficial.
In the case of WSDM Metrics, it would not be used without the presence of performance metrics so it does not make sense to extract yet another WSDL. With WSDM Identity, you could argue that WebServer is the foundation for all of the resource types you are working on, so you might as well include common definitions like WSDM Identity inside it. But only if the project became larger and incorporated more disparate resource types do you really need to extract the basic WSDM definitions into a separate WSDL.