4-3 Database Management System

A database management system (DBMS) provides a number of functions to create, edit, manipulate and analyse spatial and non-spatial data in the applications of a GIS.

Major functions of a database are as follows :

- creating records of various data types; integer, real, character, data, image etc.
- operations ; sort, delete, edit, select etc.
- manipulation ; input, analysis, output, reformatting etc.
- query ; will be made by a standardized language such as SQL (Satandard Query Language)
- programming ; will be useful for application programs
- documentation ; metadata or description of the contents of the database should be complied.

There are four types of database models :

- hierarchical model
- network model
- relational model
- object oriented model

Although all four types are used, the relational model has been most successful in GIS. Well known relational databases include dBase, Oracle and Info. Object oriented model is a new concept that has been recently developed.

Threre has been debate on which of the two-layers or object oriented is efficient in GIS. Layers may be efficient for natural resources management, for example with different layers of land use, soil, geology, agriculture, forests etc.

On the other hand object orientation may be more convenient for facility management with grouped attributes.

Figure 4.3 shows the concept of four types of database model.