Today is the age of Information. Information in today’s world is considered a valuable asset that can be bought and sold for a high price. An Information System is a manual or computerized system that is able to provide us with valuable information. The information retrieved from an information system is valuable if :-

• It reaches its correct destination.
• It reaches its destination in time.
• Its cost of collection, storage, manipulation and presentation is less.

Looking at the needs of today’s contemporary society the only way a powerful and reliable information giving system can be developed is through the integration of computer technology, manual information systems and telecommunication technology.

This integration over the years has given birth to a new technology called Information Technology. Hence information technology is a double edged innovation combining computers and manual information systems with telecommunications.

On the basis of tasks performed, two types of computerized information systems can be identified :-

• Transaction Processing system.

• Decision Support System.

In transaction processing system, emphasis is placed on recording and manipulating the occurrence of operations. e.g. banking and airline reservation systems. Transaction processing systems, whether they operate in on-line or batch mode can be update or retrieval oriented and are based on clearly defined procedures.

In decision support system the emphasis is on manipulation, analysis and particularly modeling for the purpose of supporting decision makers such as company managers, politicians and government officials. Decision support systems are also used in tactical warfare and market analysis.

Now Geographic Information Systems (GIS) are seen by many as special cases of decision support information system, wherein information is derived from interpretation of data which are symbolic (numerical) representations of features.

There are four basic approaches to defining and separating GIS from other type of information systems. This is because of the comparative recency, rapid rate of development, commercial orientation and diversity of GIS. The four approaches are as follows :-

• The process or function oriented approach.

• Application approach.

• The toolbox approach.

• The database approach.

The process or function oriented approach emphasizes the information handling capabilities of GIS. It states that GIS is a system for capturing, storing, checking, manipulating, analyzing and displaying data that are spatially (graphically) referenced to earth.

The application approach divides information system on the basis of problems. Hence if GIS has been programmed to deal with waste land development, it will be called as waste land development information system. Similarly alternative names of GIS are:-

• Natural resource information system.

• Market analysis information system.

• Urban planning information system.

• Traffic Flow planning information system

The only link between these areas is that they share common technology and methods.

The toolbox approach emphasizes the generic aspects of GIS and states that it is a powerful set of tools for collecting, storing, retrieving at will, transforming and displaying spatial data from real world.

The database approach is probably the most widely used because of the influence of database theory and practice on GIS. It states that GIS is a special case of information system where database consists of observations on spatially distributed features, activities or events that are definable in space as points, lines or areas. A GIS manipulates data about these points, lines and areas to retrieve data for ad hoc queries and analysis.

All the approaches discussed above however have a single common feature namely that GIS are systems that deal with spatial (geographical) information. It is important to note here that the term spatial refers to any type of information about location and can include engineering and remote sensing as well as cartographic information. On the other hand geographical refers only to locational information about the surface or near surface of the earth at real world scales and in real world space.

Information systems like computer aided designing (CAD), computer cartography, database management and remote sensing have substantially contributed to the development of GIS. GIS is in fact a subset of these systems. GIS also has other features that these information systems do not have, some of them being analytical operations, modeling, spatial data searching, integration etc.

Today there are a great deal of companies claiming their products to be GIS based. The annual survey of GIS WORLD (a magazine) shows that much of these products are developed to sophisticated levels with differences in organization and capabilities. Inspite of these variations three basic designs have evolved.

File processing :- each data set and function is stored as separate file and these are linked together during analytical operations. e.g. IDRISI and MAP.

Hybrid Design :- Attribute data are stored in RDBMS and separate bespoke software is used for geographical data. e.g. ARC/INFO (marketed in India by ESRI India, a joint venture between NIIT and ESRI.).

Extended Design :- Both the attribute as well as the geographical information is stored in a DBMS. e.g. SYSTEM9.