On page number 152 of OpenMaxAL doc, the heading of API is misprinted. It should be QueryNumSupportedInterfaces(), not QueryNumberSupportedInterfaces().
On page number 153, in parameters list of QuerySupportedInterfaces(), for objecteID it is mentioned that if engine does not support the identified object this method will return XA_RESULT_NOT_SUPPORTED. This return type is not in the XA_RESULT macro. It should be XA_RESULT_FEATURE_UNSUPPORTED as given in QueryNumSupportedInterfaces().