What is database ?

The word database is a composition of "data" and "base". "Data" are facts of the real world, which is supplied by "base". The word "data base" was first used in the beginning of 1960's, then written as "data-base" and recently "database".

There is another word, file, in the meaning of collection of facts of the real world. However, a file is an accumulation of data of the same kind of structure. On the other hand, a database is an integration of different kind of data.

This concept of database is deeply concerned with the development of computers. The computers were getting regarded as information processing machines rather than machines that calculate. As a result, people demanded to use computers to store fastly increasing data of the real world and utilize them communally with ease. For multi-purpose use, not file systems but database managemant systems(DBMS) were expected powerful in this sense. The purposes of database systems are as follows.

• to store enormous amount of data efficiently
• multi-purpose utilization of data
• effective and easy utilization of data

In case of knowledge information processing, data are more complex.

There are following good points from the view point of using integrated data communally as databases.

• Redundancy of data decreases due to integration and multi-purpose use of data
• Unnecessary to keep redundant data consistent
• Easy to protect data from attacks of users without access capabilities
• Unnecessary to create the same data for each program

Then, what fuctions of databases are required ? Let's start with the universal and basic functions.

1. Data Definition Language or DDL to represent integrated information of the real world
2. Data Manipulation Language or DML to manipulate information in databases
3. Data independence to reduce influence on programs when data changes not only in contents but also in structures
4. Concurrency control to keep consistency of data when updated by plural users or user programs at the same time
5. Integrity constraints to justify the contents of databases, which are not given to each user but to databases in order to prevent redundancy and omissions
6. Recovery from database destruction on account of hardware, software and human errors or accidents

These functions are impremented as the basic ones in Kappa.