14 constraints. The various database models can be specified into thee groups: object-based
logical models, record-based logical models, and physical models.
2.2.3 Geographic Information System
A Geographic Information System GIS is a specific information system applied to geographic data and mainly referred to as a system of hardware, software and procedures
designed to support the capture, management, manipulation, analysis, modeling and display of spatially-referenced data for solving complex planning and management problems
Burrough, 1986. A geographical Information System GIS is a powerful for handling spatial data. It is used for storing, retrieving, maintaining, manipulating, analyzing, and
producing the digital format of spatial data. Moreover, it could produce a spatial data in a hardcopy format Aronoff, 1991.
In GIS environment, there are two types of common data that should be taken into account, i.e. spatial data and non-spatial data. Spatial data provides information about the
feature referred to geographical orientation, size, and relative position from other features. Non-spatial data is complementary information to spatial data, which provides some further
information. Since GIS has been introduced in 1960 and due to the user demand for mapped data focused attention on data availability, accuracy, and standards, as well as data
structure issues, GIS has served an important role as an integrating technology. The capability in providing data spatial and non-spatial that are cannot be fulfilled by another
application, considering GIS, as an application for a user needs. The ultimate need, GIS has been linked to models, decision support systems and expert systems in order to make these
tools applicable in spatially explicit planning and decision-making.
15 GIS applications have been developed for wider application of digital data;
encourage more sectors to invest in GIS technology that can be run on their existing computer. The growth of GIS application has been paralleled by the extraordinary gains of
computer performance. Furthermore, the range of commercially available products of information technology that candidate for the implementation of a GIS has widened,
including CAD computer assisted drafting, DBMS database management system, geo- processing, remote sensing, GPS global positioning system, Multimedia, network
communication and EDI electronic data interchange. There are three important stages of working with geographic data de By, 2000:
1 Data entry. The early stage in which data about the study phenomenon is collected and
prepared to be entered into the system. 2
Data analysis. The middle stage in which collected data is carefully reviewed, and for instance, attempts are made to discover patterns.
3 Data presentation. The final stage in which the results of earlier analysis are presented
in an appropriate way. Data GIS demonstrated the advantage of organizing, managing, and distributing
geographic information culled from various databases while maintaining data integrity and focusing on project direction. In the framework of decision making perception, GIS
evolves around its decision support capabilities including query functions, statistical analysis capabilities, spreadsheet analysis, graphics and mapping function for evaluating
decision options and assessing the optimal and most suitable alternative United Nations, 1996.
16 GIS is gaining importance and widespread acceptance as a tools for decision support
in land, infrastructure, resources, environmental management and spatial analysis, and in urban and regional development planning. With the development of GIS, environmental
and natural resource managers increasingly have at their disposal information systems in which data are more readily accessible, more easily combined and more flexibly modified
to meet the needs of environmental and natural resource decision making. It is thus reasonable to expect a better informed more explicitly reasoned, decision-making process.
But despite the proliferation of GIS software systems and the surge of public interest in the application of the system to resolve the real world problems, the technology has commonly
seen as complex, inaccessible, and alienating to the decision makers Sharifi, 2002.
Table 2. Computerized support for decision making adopted from Turban, 1995
Phase Description
Traditional Tools Spatial
Tools
Early Compute, “Crunch Numbers”,
Summarize, Organize Early computer programs,
Management Science Models Computerized
Cartography Intermediate Find, Organize Display Decision
Relevant Information Database Management System,
MIS Workstation
GIS Current
Perform Decision relevant computations on decision relevant information:
organize and display the results, Query based and user friendly approach, “What
If “ analysis Financial Models, Spreadsheets,
trend, exploration, operations research models, Decision
Support System Spatial
Decision Support System
Spatial Decision Support System SDSS can therefore be seen as an important subset of DSS, whose potential for rapid growth has been facilitated by technical
developments Table 2. The availability of appropriate inexpensive technology for
manipulating spatial data enables SDSS applications to be created. The benefits of using GIS based systems for decision making are increasingly recognized. There is evidence that
17 GIS software is becoming increasingly suitable for use as a generator for a SDSS. As GIS
designers gain a greater awareness of decision-making possibilities, their systems will be designed to facilitate interaction with models. GIS software provides a sophisticated
interface for spatial information. Even limited functionality GIS software will provide the ability to zoom and to display or highlight different features. GIS provides database support
that is designed to allow for the effective storage of spatial data. Furthermore GIS software provides a link between the interface and database to allow the user to easily query spatial
data.
2.3 Industrial Pollutions
