A Study on Database Gateways in LAN

本研究的目的是研究和实现一个网关系统，该系统使连接到局域网的工作站能够联机访问远程信息检索系统。目前，日本大学的几个计算机中心为大学生提供信息检索服务。这些服务中的一个问题是中心使用不同的操作系统和信息检索系统，因此用户必须学习不同的数据库查询语言来获取信息。该网关系统位于终端用户和数据库服务中心之间，作为一个信息格式转换器，为用户提供一个统一的、集成的接口，吸收了数据库中心之间数据库查询语言的差异，其中一个工作站被用作以太网局域网的网关机。在该网关上实现了两种通信协议。第一种是CCITT X.3/X.29协议，第二种是基于TCP/IP的协议。考虑到将来基于TCP/IP的网络在日本大学环境中的扩展，TCP/1 P将被更广泛地接受。该网关使局域网中的任何工作站都可以自由地访问远程数据库中心。目前，Nacsis的科学信息网采用48 kbps的X.25线路，并以Widow-based系统为例，实现了对文献数据库的全文/快速图像检索，以演示通过网关系统访问同类数据库。

The aim of this study was the research and implementation of a gateway system which enables on-line access to remote information retrieval systems from the workstations attached to the local area network.Now several computer centers in Japanese universities provide information retrieval services for university people. One of the problems in such services is that centers uses different operating systems and information retrieval system ; thus users have to learn different database query language to get information. This makes the utilization of databases difficult for casual users.The proposed gateway system is positioned between end-users and database service centers and functions as an information format converter in order to provide a unified and integrated interface to users, absorbing the differences of DB query languages among database centers.One of the workstations was employed as a gateway machine to the Ethernet-based LAN. Two communication protocols were implemented on this gateway. The first one is CCITT X.3/X.29 ; the other one is TCP/IP based protocol suite. Considering the future expansion of TCP/IP based networking in Japanese university environment, TCP/1P will be accepted much more widely. This gateway has made it possible for any workstations in the local area network to access freely to remote database centers. At present, 48kbps X.25 line is used for this purpose in Nacsis's Science Information Network.A prototype software was made to achieve full-text/faster image search for document database as a widow-based system in order to demonstrate homogeneous database access through gateway systems.