Autonomous concurrent objects can be regarded as message receivers rather than labeled records by message senders, each having object references. The subtype relation on reference types can be determined by judging how various messages can be understood. Based on this idea, this paper presents a type system and compilation techniques for concurrent objects, implementing efficient pattern matching of first class messages, where the look-up can be performed as direct indexing of a small table, and the table size can be bounded by a number slightly more than the number of injection tags which the message value may have.