When same operation is defined in Service level as well as module level, service level operation should be used.

Module operations will be added to the services for which the module is engaged. Since module operations are global for all the services engaging it, it is natural to overwrite operation settings in service.xml. For example, if security policy is given in module level operation and if a particular service wants to give a different policy to that operation, we should be able to define same operation in service.xml with different security policy. In such cases, policy defined in service.xml should be used.