A method of processing a digital service signal and an apparatus thereof are disclosed. The present invention includes executing a primary application for the digital service signal, wherein the primary application is a triggered application or a non-triggered application, transmitting messages of interactive services for a secondary application associated with the primary application, wherein the interactive services includes a first mode related to the triggered application or a second mode related to the non-triggered application, receiving a request for descriptions identifying the interactive services, transmitting the descriptions having service id information identifying each of the interactive services and service type information indicating a type of the each of the interactive services, and providing the interactive services by transmitting information for the interactive services.