2. Introduction

It can be safely assumed that databases with a high volume of data or a complicated relational setup (like, perhaps, a lexical database for a living language) must be accessible to many users and operators at the same time. Ideally, it should be possible to use existing different hardware and software platforms that can be combined into the actual system. In order to reduce the implementation cost, only one system, the database server, needs to be powerful; the user stations typically just display data and accept user commands, but the processing is done on one machine only which led to the name client-server database. In addition, the user interface should be easy to maintain and should require as little as possible on the client side.

A system which meets these criteria can be built around the following items of protocols, concepts and software:

Linux

supplies the operating system. It is a stable Unix implementation providing true multi-user multi-tasking services with full network (TCP/IP e. a.) support. Except from the actual media and transmission cost, it is available free of charge and comes in form of so-called distributions which usually include everything needed from the basic OS to text processing, scripting, software development, interface builders, etc.

HTML

is the Hypertext Markup Language used to build interfaces to network systems like Intranets and the WWW, the World Wide Web. HTML is very simple and can be produced with any ASCII-capable text editor.

Browsers

are text-based (e. g. Lynx) or graphical (e. g. Mosaic, Netscape, Arena etc.) applications accepting, evaluating and displaying HTML documents. They are the only piece of software which is directly operated by the database user. Using browsers, it is possible to display various types of data (text, possibly images) and communicate with http servers (see next) on about every popular computer model for which a browser has been made available.

http servers

provide access to the area of a host computer where data intended for public use in a network are stored. They understand the http protocol and procure the information the user requests.

SQL

Structured Query Language is a language for manipulating data in relational databases. It has a very simple grammar and is a standard with wide industry support. SQL-based databases have become the core of the classical client/server database concept. There are many famous SQL systems available, like Oracle, Informix etc., and then there is also msql which comes with a very low or even zero price tag if it is used in academical and educational environments.

CGI

Common Gateway Interface is the programming interface between the system holding the data (in our case an SQL-based system) and the network protocol (HTML, of course). CGIs can be built around many programming languages, but a particularly popular language is perl.

perl

is an extremely powerful scripting language which combines all merits of C, various shell languages, and stream manipulation languages like awk and sed. Perl has a lot of modularized interfaces and can be used to control SQL databases, for example.