To develop distributed applications requires to consider not only functional requirements but also non-functional requirements such as distributions, synchronizations, and scheduling policies. Specifying such non-functional requirements is necessary for supporting on-line capabilities of Autonomous Decentralized Systems (ADS). However, the existing design notations and methods do not address such needs sufficiently enough to develop ADS applications systematically using object-oriented technique. In this paper, we propose an object-oriented design-level support for specifying concurrent, distributed, and autonomous object behaviors in developing dynamic distributed applications. We develop a high-level meta-object protocol called diMOP to deal with object distributions, method synchronizations, and method scheduling policies. In addition, we develop Class Diagram Supporting diMOP (CDSM) and Dynamically Configurable Object Statemachine (DCOS) for specifying non-functional behaviors and dynamic configuration behaviors, by extending the ordinary class diagram and state diagram of UML. A development environment called diMOPer is implemented to support our approach.

This paper describes the Profit-Sharing, a reinforcement learning approach which can be used to design a coordination strategy in a multi-agent system, and demonstrates its effectiveness empirically within a coil-yard of steel manufacture. This domain consists of multiple cranes which are operated asynchronously but need coordination to adjust their initial plans of task execution to avoid the collisions, which would be caused by resource limitation. This problem is beyond the classical expert's hand-coding methods as well as the mathematical analysis, because of scattered information, stochastically generated tasks, and moreover, the difficulties to transact tasks on schedule. In recent few years, many applications of reinforcement learning algorithms based on Dynamic Programming (DP), such as Q-learning, Temporal Difference method, are introduced. They promise optimal performance of the agent in the Markov decision processes (MDPs), but in the non-MDPs, such as multi-agent domain, there is no guarantee for the convergence of agent's policy. On the other hand, Profit-Sharing is contrastive with DP-based ones, could guarantee the convergence to the rational policy, which means that agent could reach one of the desirable status, even in non-MDPs, where agents learn concurrently and competitively. Therefore, we embedded Profit-Sharing into the operator of crane to acquire cooperative rules in such a dynamic domain, and introduce its applicability to the realistic world by means of comparing with RAP (Reactive Action Planner) model, encoded by expert's knowledge.

A lattice system in this paper is a system whose components are ordered like the elements of (m, n) matrix. A representative example of a lattice system is a connected-(r, s)-out-of-(m, n):F lattice system which is treated as a model of supervision system. It fails if and only if all components in an (r, s) sub lattice fail. We modify the lattice system so as to include a maintenance action and a restriction on the number of failed components. Then, this paper presents availability and MTBF of the repairable system, and reliability when the system stocks spare parts on hand to ensure the specified reliability level.

A large-scale primarily public system requires in addition to high reliability, a broad range of applications from control to information services. As construction is phased-in this system must be flexible, changeable and able to grows as the needs arise. However, a changing a system may lead to loss of reliability. A system that is able to change and grow in a reliable and stable manner is called an assurance system and the technology it uses is called assurance technology. This paper describes the basic technology, phased-in system construction and so on of assurance technology based on an autonomous decentralized system. It further discusses application of assurance technology to ATOS as an example of a large-scale transport operation control system. Note: ATOS; Autonomous Decentralized Transport Operation Control System

More than forty thousands computer viruses have appeared so far since the first virus. Six computer viruses on average appear every day. Enormous expansion of the computer network opened a thread of explosive spread of computer viruses. In this paper, we propose a distributed approach against computer virus using the computer network that allows distributed and agent-based approach. Our system is composed of an immunity-based system similar to the biological immune system and recovery system similar to the recovery mechanism by cell division. The immunity-based system recognizes "non-self" (which includes computer viruses) using the "self" information. The immunity-based system uses agents similar to an antibody, a natural killer cell and a helper T-cell. The recover system uses a copy agent which sends an uninfected copy to infected computer on LAN, or receives from uninfected computer on LAN. We implemented a prototype with JAVATM known as a multi-platform language. In experiments, we confirmed that the proposed system works against some of existing computer viruses that can infect programs for MS-DOSTM.

In cellular systems, autonomous reuse partitioning (ARP) is one of the channel assignment strategy which attains the high spectral efficiency. In the strategy, the movement of mobile stations (MSs) causes the disturbance of reuse partition. Furthermore the smaller cell size causes the spectral efficiency worse. In this paper, we propose a new ARP strategy with reuse partitioning reconstructing, named RP-reconstructing ARP strategy, for microcellular systems. We evaluate the performance of the proposed strategy with blocking rate and forced call termination rate by the computer simulation. The results show that the system with the proposed strategy accommodates 1.5 times as many users as the system with ARP does.

Designing control and robotic systems as autonomous decentralized systems introduces a new degree of flexibility in the manufacturing and in the application of such systems. This flexibility is required for the systems to work in environments that are not totally predictable and that can change dynamically. In this paper, we present a new concept for real-time communication that supports this flexibility while still preserving real-time guarantees for hard real-time communication. The concept is designed to work on multiple-access busses. In particular, we consider its application on wireless local area networks and field-busses. The concept addresses requirements of hard-real time, soft real-time and non real-time communication. For this, we extend the TDMA (time- division multiple-access) approach for time-triggered hard-real time communication by the concept of shared channels that support event-triggered communication and coexist with hard real-time channels. A first implementation of concept has been carried out in the context of the CAN-bus.

Migration transparency is considered in the context of multi-agent systems. A mobile agent architecture is proposed with an Availability service and a Transparency interface. We define mobility as explicit (or proactive) when the agent decides when and where to move and define mobility as implicit (i. e. , transparent or reactive) when it is a consequence of changes in the environment. Implicit mobility of agents is explored in addition to the usual explicit mobility. The search for a target agent (or agency) follows a transparent location and selection. The client agent preferably moves towards the target agent. If not possible, the target agent will move towards the client agent when calling back. If both agents can not move then the execution takes place remotely or is abandoned. Transparency is goal oriented.

The purpose of this note is to carry out study on a 3-out-of-4:G warm standby system with nonidentical components. By using Markov model, the general form solution of stationary availability of the system is obtained. Examples are given to illustrate the solutions of transient and stationary availability of such system.

The Mobile Agent technology helps in the development of applications in open, distributed and heterogeneous environments such as the Internet and the Web, but it has to answer to the requirements of security and interoperability to achieve wide acceptance. The paper focuses on security and interoperability, and describes a Secure and Open Mobile Agent (SOMA) programming environment where both requirements are main design objectives. On the one hand, SOMA is based on a thorough security model and provides a wide range of mechanisms and tools to build and enforce flexible security policies. On the other hand, the SOMA framework permits to interoperate with different application components designed with different programming styles. SOMA grants interoperability by closely considering compliance with the OMG CORBA and MASIF standards. SOMA has already shown the feasibility and effectiveness of the approach for the development of flexible and adaptive applications in several areas, particularly in network and systems management.

Packet concentrators are used in many high-speed computer communication systems such as fast packet switches. In these systems, the time available for concentration is very short. It is therefore desirable to realize the packet concentrators as hardware chips for fast concentration. The knockout concentrator was proposed for hardware realization. In this paper, we improve this concentrator to reduce the probability of packet loss, and the improved concentrator is called wraparound knockout concentrator. This concentrator has several wraparound paths within it, and it does not require any additional pin per chip. After contention among the packets in a slot, each winner goes to a distinct output, some losers circulate along the wraparound paths for contention in the subsequent slot, and the remaining losers are discarded. In this manner, some losers are not discarded immediately and they still have the chance to go to the outputs in the subsequent slot, thereby reducing the probability of packet loss. We analyze the number of logic gates required and the probability of packet loss. The numerical results show that if the proposed concentrator has a few wraparound paths, the probability of packet loss can already be reduced by orders of magnitude.

We deal here with diagnosis for failures of series/parallel structure system. The conventionals have assumed that the system failure is caused by a single minimal cut set (MCS). The purposes of this paper are to propose a new diagnosis method to identify all MCSs by utilizing the series/parallel structure and repair information without requiring an excessive number of inspections. Moreover, by applying our method to several types of series/parallel structure system, and to system having some kinds of probability distributions, desirable system for our method are persuaded. We evaluate not just the number of inspections but also the cost of diagnosis, and show the condition under which our method is effective.

The present paper modifies the algorithm to estimate harmful event frequencies and examines the definition of modes of operation in IEC 61508. As far as the continuous mode concerns, the calculated results coincide with those obtained based on the standard. However, for the intermediate region of medium demand frequencies and/or medium demand durations, the standard gives much higher harmful event frequencies than the real values. In order to avoid this difficulty, a new definition of modes of operation and a shortcut method for allocation of SILs are presented.

The SDP (Sum of Disjoint Products) approach is a well-known technique for computing network reliability measures. So far several algorithms have been developed based on this approach. In this letter, we present a general framework for parallelization of these SDP algorithms. Based on the framework, we implemented a parallel version of an SDP algorithm called CAREL on a network of workstations. Experimental results show that it works fairly well with almost linear speedups.

This paper proposes a model checking method for microcomputer programs. To deal with the state explosion problem, we adopt a compositional verification approach. Based on the proposed method, a microcomputer program for a real-life air-conditioner is verified. The program is large enough to cause state explosion. Among fourteen typical properties of the program, five properties are successfully verified by our method.

For cluster systems consisting of multiple processing nodes and shared servers which consist of an on-line and a backup shared server, we propose a hot-standby scheme for shared servers. In this scheme for shared servers, when the on-line shared server receives a command from a node, it sends only an update command and its data identifier to the backup shared server. Both the on-line and the backup shared server execute the update command independently, and the command result of the on-line shared server is identical to that of the backup shared server. When the on-line shared server fails, the backup reconstructs the shared data by using its own shared data and the user data from each node. We evaluated the system recovery time and the performance overhead for this hot-standby scheme. It enables the performance overhead to be ignored, and the system recovery time to be shortened to 20 seconds in cluster systems.

Hash routing is an algorithm for a distributed WWW caching system that achieves a high hit rate by preventing overlaps of objects between caches. However, one of the drawbacks of hash routing is its lack of robustness against failure. Because WWW becomes a vital service on the Internet, the capabilities of fault tolerance of systems that provide the WWW service come to be important. In this paper, we propose a duplicated hash routing algorithm, an extension of hash routing. Our algorithm introduces minimum redundancy to keep system performance when some caching nodes are crashed. In addition, we optionally allow each node to cache objects requested by its local clients (local caching), which may waste cache capacity of the system but it can cut down the network traffic between caching nodes. We evaluate various aspects of the system performance such as hit rates, error rates and network traffic by simulations and compare them with those of other algorithms. The results show that our algorithm achieves both high fault tolerance and high performance with low system overhead.

Knowledge-based program understanding is widely known as one of the key issues in programming education support systems and environments for novices. Most program understanders, however, have limitations. One of them is an ability to deal with a single programming language, while human tutors can comprehend plural languages by means of generalized knowledge on programming languages and techniques. This paper proposes the concepts and methodology of the knowledge-based program understander ALPUS II, which deals with plural programming languages, i. e. , Pascal and C, by means of generalized abstract syntax AL and knowledge representations based on it. ALPUS II is an extension of ALPUS, which dealt with a single programming language Pascal, and is a sub-system of an intelligent programming environment INTELLITUTOR. The INTELLITUTOR system consists of a guided programming editor GUIDE and a knowledge-based program understander ALPUS II, and is available on the Internet. In the process of comprehension source statements written in Pascal or C are translated into AL representation first. Since the contents of the programming knowledge bases are adjusted to deal with the AL representations the program comprehension procedure is available for both Pascal and C. It is possible to append other programming languages by simply attaching a transformation module for each additional procedural language. It is noted that knowledge acquisition tasks for additional languages are not needed since the contents of the knowledge base are generalized for multiple use. The INTELLITUTOR system was implemented in the frame-based knowledge engineering environment ZERO on a UNIX server machine in the Internet environment. ALPUS II demonstrates interesting features in program comprehension for the C language by means of the transformed knowledge from the already available knowledge for Pascal, which was developed for ALPUS, in a feasibility study. The current version of ALPUS II supports almost full specifications for Pascal and a Pascal-associated subset for C. This limitation should be reasonable for programming practice at freshmen classes of a university.

We present an architecture of a VOD system employing proxy servers. The proposed VOD system provides efficient and reliable VOD services and solves the problems caused by traditional VOD systems of centralized, hierarchical or distributed architecture. The proxy servers are placed between video servers and user systems. The proxy server is a small size video server that has not only caching function but also intelligence such as VCR-like video stream control or navigation of other proxy/video servers to search for a selected video program. Using a VOD system of the proposed architecture, the VOD services can be provided to more users because it reduces the workload of video servers and network traffic. We provide the performance model of the system. Service availability is also analyzed. The proposed architecture shows better performance and availability than the traditional VOD architectures.

We consider the performance of hyperelliptic curve cryptosystems over the fields Fp vs. F2n. We analyze the complexity of the group law of the jacobians JC(Fp) and JC(F2n) and compare their performance taking into consideration the effectiveness of the word size (32-bit or 64-bit) of the applied CPU (Alpha and Pentium) on the arithmetic of the definition field. Our experimental results show that JC(F2n) is faster than JC(Fp) on an Alpha, whereas JC(Fp) is faster than JC(F2n) on a Pentium. Moreover, we investigate the algorithm of the jacobian and the definition-field arithmetic to clarify our results from a practical point of view, with theoretical analysis.