1.1.5 Core and Optional Protocols

To facilitate transaction coordination, the system supports a set of core protocols and a set of optional protocols, as described in the Protocol Summary (section 2.2). Core protocols are proprietary to the system and are used by default by applications, application services, and resource managers. Optional protocols allow interoperability through transaction processing industry standards. Relevant industry standards are listed in section 2.1.7. Applications, application services, resource managers, and transaction managers that are communicating with the system over optional protocols are referred to as external applications, external application services, external resource managers, and external transaction managers. The system allows the possibility of processing a transaction by using only a single core or optional protocol, or a combination of core and optional protocols.