All service operations on a SwitchYard service can define Input, Output and Fault messages. These messages have a type associated with them, which is defined as a QName. This type is used by the data transformation layer, when trying to work out which transformers to apply to a message payload.

For Bean services, the default type QName for Input (input param), Output (return value) and Fault (Exception) are derived from the Java class name in each case (param, return, throws). For some types however (such as org.w3c.dom.Element), the Java type name alone does not tell you the real type of the data being held by that Java Object instance. For this reason, Bean service operations (methods) can be annotated with the @OperationTypes annotation.