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In distributed databases, oriented toward general business software such as groupware, the asynchronous update method is widely used in order to align the databases. In this method, each database has replicas of the other databases, and the replicas are updated at the same time according to a predetermined replica routing schedule. This paper discusses an approximate method for minimizing the communication cost and time needed for updating the replicas in such a distributed database. More precisely, the case in which the communication cost is proportional to the amount of transferred data is considered, and an optimization problem is formulated in which the replication routing schedule minimizing the time for the replica update is to be determined from those minimizing the communication cost for the replica update. An approximate solution for the formulated problem is presented. Then the result of evaluation of the approximate replication routing schedule obtained as the approximate solution is discussed, and it is shown that the communication cost for replica update is minimized and that the time for the replica update is at most 1.2 times the minimum value if the number of distributed databases is at most 7. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 85(4): 61–70, 2002 [ABSTRACT FROM AUTHOR]

In this paper, we propose a new method for fast and efficient detection of communication protocol errors with less memory requirements and processing time when there exists an excess/deficiency of definition or deadlock in signal transmission/reception. Practically, a new method of protocol validation is presented where the protocol errors are detected by dividing the protocol inspection into two stages: one is inspection centered on the operations of each process and the second is inspection of all process operations at the same time. The characteristic of this method of validation is that in the former stage the excess/deficiency of transmission/reception is detected without enumerating the states of the whole system and in the second stage, deadlock is detected by enumerating the minimum number of system states. As a result, when the number of processes is large, the number of system states to be enumerated, can be greatly decreased as compared to the conventional methods. To evaluate the proposed method of protocol validation we present application results of various protocol examples. We show that memory requirements and processing time are greatly reduced and large-scale protocols with large number of processes which could not be fully inspected by the conventional methods, can also be validated completely. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 83(7): 26–39, 2000 [ABSTRACT FROM AUTHOR]

In distributed databases for general-purpose business software, such as groupware, the asynchronous replication update method is widely employed to assure coincidence in the contents of the database; the replications of other databases retained in each database are updated simultaneously according to a predetermined schedule. This article discusses the approximate scheduling in such a distributed database that minimizes the communications cost of updating the replications. More precisely, as the first step, we consider the case in which two-way concurrent transmission is allowed in each link, and the communications cost is proportional to the communication time required for the transfer. The problem of deriving the schedule to minimize the communications cost is formulated. As a practical method of solving that problem, a heuristic method that effectively derives the approximate schedule with a communications cost close to the minimum is proposed. A quantitative evaluation of the proposed method is presented, and it is shown that a schedule very close to the optimal solution is obtained if the communications cost coefficient of the links is almost the same. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 83(1): 73–86, 2000 [ABSTRACT FROM AUTHOR]

Distributed databases in general-purpose business software such as groupware widely use a method for simultaneously updating the replicas of other databases owned by each database according to the replication routing schedule. In this paper, a replication routing schedule is discussed in which the time required for updating the replica is the minimum in the distributed database. Specifically, an optimization problem is first formulated for deriving the replication routing schedule with minimum update time. Next, in the cases of even and odd numbers of distributed databases, an algorithm providing a replication routing schedule as an optimum solution is presented in the even case, while a heuristic algorithm providing an approximate solution is shown for the odd case. These algorithms are extremely simple and are practical since the required amount of computational processing is small. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 82(2): 11–20, 1999 [ABSTRACT FROM AUTHOR]

This paper proposes a new method for efficient validation of the telecommunication protocol, containing the internal events, including those for the timer and resource management. The proposed validation method first converts the protocol containing the internal event into the equivalent protocol not containing the internal event. Then the original protocol is validated by applying the already-proposed validation method for the protocol not containing the internal event to the result of conversion. This paper discusses mainly the principle and the algorithm of the protocol equivalent conversion. The features of the proposed validation method are that the protocol is validated with the minimum processes and signals, which reduces the processing time and the memory capacity needed in the validation and also improves the efficiency. [ABSTRACT FROM AUTHOR]

This paper proposes a new protocol validation method to detect such errors as lack and redundancy in given protocol specifications. This method is characterized by the fact that it enumerates a minimum number of global system states and global state transitions that are required for the validation. This leads to a remarkable reduction in both validation tine and required memory size. Furthermore, this proposed method enables the validation of large-scale protocol specifications, which was impossible by the conventional validation methods. [ABSTRACT FROM AUTHOR]

Evaluates the use of the Escort, an environment for specifying communication requirements telecommunication software prototype. Intention of establishing efficient techniques for developing high-quality telecommunications specifications; Adoption of the Specification Description Language; Assessment of Excort functions.

For the development of communications software com- posed of many modules, protocol validation is essential to detect errors in the interactions among the modules. A number of protocol validation techniques were proposed in the past, but the validation time required by these techniques is too long for many actual protocols. This paper proposes a new fast protocol validation technique to overcome this drawback. The proposed technique is to construct the minimum acyclic form of state transitions in individual processes of the protocol, and to detect protocol errors such as system deadlocks and channel overflows fast. This paper also presents a protocol validation system based on the proposed technique to confirm its feasibility and shows validation results for some actual protocols obtained with this system. As a result, the protocol validation system is expected to contribute to a great extent to the improvement of the productivity in development and maintenance of communications software. [ABSTRACT FROM AUTHOR]