Coordination Messages Research Articles

Constructing checking sequences for distributed testing

Abstract The objective of testing is to determine whether an implementation under test conforms to its specification. In distributed test architectures involving multiple remote testers, this objective can be complicated by the fact that testers may encounter coordination problems relating to controllability (synchronization) and observability during the application of tests. Based on a finite state machine (FSM) specification of the externally observable behaviour of a distributed system and a distinguishing sequence, this paper proposes a method for constructing a checking sequence where there is no potential controllability or observability problems, and where the use of external coordination message exchanges among testers is minimized. The proposed method does not assume a reliable reset feature in the implementations of the given FSM to be tested by the resulting checking sequence.

Distributed testing without encountering controllability and observability problems

The objective of testing is to determine whether a system under test conforms to its specification. In distributed test architectures that utilize remote testers, this objective can be complicated by the fact that testers may encounter problems relating to controllability and observability during the application of a test sequence. Existing solutions to these problems involve first constructing a test sequence from the specification of an implementation under test, and then inserting coordination messages or appending selected test subsequences that prevent the occurrences of controllability and observability problems during the application of the resulting test sequence. This paper proposes a method that utilizes a set of transformation rules to construct an auxiliary directed graph from a given specification, and constructs a rural Chinese postman tour in this graph to yield a minimum-length test sequence where there is no potential controllability or observability problems, and where the use of coordination messages is minimized.

An efficient time-based checkpointing protocol for mobile computing systems over mobile IP

Time-based coordinated checkpointing protocols are well suited for mobile computing systems because no explicit coordination message is needed while the advantages of coordinated checkpointing are kept. However, without coordination, every process has to take a checkpoint during a checkpointing process. In this paper, an efficient time-based coordinated checkpointing protocol for mobile computing systems over Mobile IP is proposed. The protocol reduces the number of checkpoints per checkpointing process to nearly minimum, so that fewer checkpoints need to be transmitted through the costly wireless link. Our protocol also performs very well in the aspects of minimizing the number and size of messages transmitted in the wireless network. In addition, the protocol is nonblocking because inconsistencies can be avoided by the piggybacked information in every message. Therefore, the protocol brings very little overhead to a mobile host with limited resource. Additionally, by taking advantage of reliable timers in mobile support stations, the time-based checkpointing protocol can adapt to wide area networks.

They have their job, we have ours: Reassessing the feasibility of police‐social work cooperation

Seduced by the symbolic content of the coordination message, many senior administrators, social planners, and politicians advocate that the police and social work should work closer together. Examination of the critical properties of these occupations and of joint police‐social work programmes reveals, however, that the differences between them far outweigh their similarities. Moreover, these differences are not casual, but located in the culture and structure of each occupation, and in the structure of society as a whole. This analysis leads to the conclusion that proposed suggestions to better police‐social work relationships are unfeasible, and that it would be preferable if each occupation would simply fulfil its societal role on its own.