Resource Discovery is to find the components where the resources are offered.
Same as Discovery service, the Resource Discovery service is included in the Subsystem Manager component. Operator Control (the client) looks for subsystems by broadcasting Query Identification. The receiving Subsystem Manager responses with Report Identification, which contains the Address of the Subsystem Manager. Operator Control then sends Query Resources message to the Subsystem Manager component, which replies Report Resources that contains the URL of the registered resources.
Figure 21 Resource Discovery Message Interaction