A study of distributed database system architecture and its retrieval method

点击翻译按钮获取中文摘要

The objective of this research is to find out necessary fuctions of distributed database systems for accessing to heterogeneous molecular biology databases.To achieve this goal, we have constructed, in the first year, a proto-type database system for Genbank, Swiss-prot, PIR, and PDB.In the proto-type system, these four databases are stored in different networked workstations, and can be accessed by OQL (Object Query Language) through an object-oriented database schema.Each database has a database agent written in C and perl, and the agents commnunicate with the user agent using MPI (Message Passing Interface).We also developed a mobile agent using Agent Tcl.The agents autonomously go around the databases and collect relevant data entries.In the second year, we have changed the database agent programs to use Java applet and Horb.Users can easily access databases through web browsers that support Java.A database agent temporarily saves the retrieved data as HORB objects in itself and sends minimum data to the user agent, for example, entry names of the retrieved data.This architecture helps to suppress unnecessary data transfer, because the whole content of the retrieved entry can be sent to the user agent on demand.The time consuming operations such as alignment and aggregation can be done in CPU server workstations by sending data to them.We have good system response time.Currently, the life time period of the HORB objects in the database servers is during the session, however, it can be longer.A database agent itself can assembly multiple entries in terms of the same gene by using homology search.The security problem is yet to be studied.This problem will be faced in almost all systems using agents, because it is not clear whether the agent software surely assures the security of the operational systems.