The processes transfer_s and ack_handler have roughly the same tasks as in the reference specification in Section 2.3. The receiver part is similar in structure to the reference specification.
Since there are no common variables in LOTOS, all actions are performed at the DT-PDU buffer in the process transfer_s. It also consists of two processes CONNECT and DATA_TRANSFER for protocol phases, between which the conn and eom variable is passed.
The LOTOS XDT service specification still differs in another aspect of the other specifications.
At each point of interaction the reactions to the expected events as well as the reactions to unexpected events are described.
They contain two sub-processes CONNECT and DATA_TRANSFER representing the protocol phases. The process association connects the two service access points and transports the data of XDATrequ-primitives from the transmitter to the receiver, where they are passed as XDATind-primitives to the recipient.
The association process is connected to the transmitter and receiver processes by the non-visible Gates SA and RA. Two data types are introduced: Data Type and SPType.
XDT service specification The XDT service specification describes the behavior of the service interface with the service access points Sender_SAP and Receiver_SAP, referred to as S and R.
The specification uses the resource-oriented style, because thereby the dependencies between the processes at the service access points can be illustrated in more detail.
The sender and receiver processes are each composed of three sub-processes.
The sub-processes CONNECT and DATA_TRANSFER each describe the connection set-up and data transfer phase.
The specification consists of the three main processes sender, association and receiver (see Figure 1).