This part of ISO/IEC 10026: a) provides a general introduction to the concepts and mechanisms defined in ISO/IEC 10026; b) defines a model of distributed transaction processing; c) defines the requirements to be met by the OSI TP Service; and d) takes into consideration the need to coexist with other Application Service Elements, e.g. RDA (Remote Database Access), ROSE (Remote Operations Service Element), and non-ROSE based applications. This part of ISO/IEC 10026 makes sufficient provisions to allow the specification of transaction-mode communications services and protocols that meet the properties of: atomicity, consistency, isolation, and durability (the ACID properties), as defined in ISO/IEC 9804. This part of ISO/IEC 10026 does not specify individual implementations or products, nor does it constrain the implementation of entities or interfaces within a computer system.