This ÖVE/ÖNORM provides common elements for basic time-critical and nontime-critical messaging communications between application programs in an automation environment and material specific to Type 13 fieldbus. The term "time-critical" is used to represent the presence of a time-window, within which one or more specified actions are required to be completed with some defined level of certainty. Failure to complete specified actions within the time window risks failure of the applications requesting the actions, with attendant risk to equipment, plant and possibly human life. This standard specifies interactions between remote applications and defines the externally visible behavior provided by the Type 13 fieldbus application layer in terms of a) the formal abstract syntax defining the application layer protocol data units conveyed between communicating application entities; b) the transfer syntax defining encoding rules that are applied to the application layer protocol data units; c) the application context state machine defining the application service behavior visible between communicating application entities; d) the application relationship state machines defining the communication behavior visible between communicating application entities. The purpose of this standard is to define the protocol provided to 1) define the wire-representation of the service primitives defined in IEC 61158- 5-13, and 2) define the externally visible behavior associated with their transfer.