| Research Abstract |
This research is composed of three parts : Concurrency Control of Multiversion Databases Based on Workflows, Cooperative Works on Digital Contents Management, and Cooperative Work for Moving Objects.
In the first part, we discuss the effect on concurrency control in cooperative databases using the consistency information expressed by workilows. Cooperative works require to record multiversions, to make users possible read any necessary versions, and to avoid rollback. In a mukiversion database, which has versions of data, a set of data is consistent if and only if it is created following the workflow. We show that the concurrency control of multiversion databases can be carried out efficiently without rollback Such consistency information is also useful to satisfy the requirement of reading the latest versions.
We also consider the effect on cooperative databases by consistency information such as worktlows and report a prototype system implemented by the CAD system MicroSim DesignLab. U
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sing the consistency information, we showed that both consistency management requirements from users and database systems can be satisfied.
In the second part, we discuss the problems of how to use XML technologies to cooperate the works of creating digital contents and to manage created digital contents. We use the XML technologies to extend an e-learning system developed by us before. This system is an integrated e-learning management system on WEB. It can support various needs both from teachers and students and has been used in the education of several universities.
In moving object databases, object locations in some multi-dimensional space depend on time. In this part, we investigate logical properties of moving objects in connection with queries over objects using tools from differential geometry. In an abstract model, object locations can be described as vectors of continuous functions of time. Using this conceptual model, we examine the logical relationships between moving objects, and between moving objects and (stationary) spatial objects in the database. We characterize these relationships in terms of position, velocity and acceleration. We show that these fundamental relationships can be used to describe natural queries involving time instants and intervals. Less
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