Such usage can be initiated by a user, or as a result of the interaction between the application and the user. This is much more complicated usage of channels. For such complicated usage, Recommendation ITU-R BT.2037 [10.12] defines what an IBB system is and how an IBB system should behave. Recommendation ITU-R BT.2053 [10.3] defines technical requirements of IBB systems highlighting a broadcast centric scenario, which is also based on the enhanced use of the return interaction channel. Such formats allow the creation of a shared base for organization of content management and exchange in different implementations of interactive system applications by identifying functional commonality among the declarative application environments for interactive TV application specifications ACAP-X, BML and DVB-HTML.