Shigenari Nakamura

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Application processes have to be efficiently performed in presence of server faults in a cluster. Multiple replicas of a process are performed on multiple servers. However, the more number of replicas of a process are performed, the more reliable and available the process can be performed but the more amount of electric energy is consumed. In this paper, we(More)
In information systems, data in an object may illegally flow into another object if a subject manipulates the objects. In this paper, we discuss information flow control models to prevent illegal information to occur in the role-based access control (RBAC) model. First, we define a legal information flow relation r<sub>i</sub>&#x21D2; r<sub>j</sub> among(More)
In information systems, data in an object may illegally flow into another object if transactions manipulate the objects. In our previous studies, the role-based synchronization (RBS) and object-based synchronization (OBS) protocols are discussed to present illegal information flow in the role-based access control (RBAC) model. Illegal read operations mean(More)
In information systems, data in an object may illegally flow into another object if transactions read and write the objects. A transaction illegally reads an object if data in objects which the transaction is not allowed to read are stored in the object. In addition, it is specified data in which object is allowed to flow to other objects. A suspicious(More)
In a peer-to-peer (P2P) type of topic-based publish/subscribe (P2PPS) model, each peer (process) caP2P) typen be a publisher and subscriber. Here, a peer publishes an event message and then the event message is notified to a target peer which is interested in the event message. Publications and subscriptions are specified in terms of topics. In the(More)
In distributed applications, a group of multiple processes are cooperating with one another by exchanging messages in networks. Information systems like cloud computing systems are getting scalable, which are composed of a huge number of processes. We assume a physical clock which each process reads is synchronized with a time sever, i.e. maximum offset of(More)
A distributed system is considered in an event-driven model composed of processes which are sequences of events. In this paper, we discuss a peer-to-peer (P2P) model of a topic-based publish/subscribe system (P2PPS model) where each peer process (peer) can both subscribe interesting topics and publish event messages. Since each peer can both publish and(More)
A publish/subscribe (PS) model is an event-driven model of a distributed system. In this paper, we consider a peer-to-peer (P2P) type of PS model where each peer (process) can publish and subscribe events. Here, a peer publishes an event message and then the event message is notified to a target peer which is interested in the event. Publications and(More)
Data in an object may flow into another object if transactions read and write data in the objects. A transaction illegally reads data in an object if the object includes data in other objects which are not allowed to be read. In our previous studies, the flexible read-write-abortion with role sensitivity (FRWA-R), object sensitivity (FRWA-O), and role(More)