The latest advancement of object oriented data modelling in GIS and computer aided design has opened an opportunity in data modeling. Although object oriented data modelling has been developed in GIS realm long before its CAD counterpart, it has never been design oriented since GIS was not initially developed for spatial design purposes. Through data modelling which have entered a new dimension in object oriented data modelling, we can design a specific type of database to support the GIS application.
Object oriented modelling allows us to define our own types of objects through topological, spatial, and general relationship which can help capture how these object interact with other object.
What is GIS?
A Geographic information system is the combination of skilled persons, spatial and descriptive data, analytic method, and computer software and hardware- all organized to automate, manage, and deliver information through geographic presentation.
GIS software: a geographic database
The key concept to grasp about GIS software is that it is a geographic database management system.
Geodatabases are implemented directly on commercial relational or object relational database management system. A GIS extends an object relational database so that it can efficiently store geographic data, produce maps and perform spatial analytic tasks. The geodatabase supports multiple format of spatial data including-
-simple file features (such as shape files)
-custom features with business logic and editing rules
-attribute data
-raster/grid data
-CAD data.
Object oriented database
A data model is a collection of conceptual tools for describing data, data relationships data semantics and consistency constraints. The object oriented data model is based on the object oriented programming language paradigm, which is now in wide use. Inheritance, object identity and encapsulation (information hiding), with method to provide an interface objects, are among the key concepts of object oriented that have found applications in data modeling. The object oriented data
model also supports a rich type system including structural and collection types. The advantages of object oriented database management are:
– Designer can specify the structure of objects and their behavior (methods)
– Better interaction with object- oriented languages such as java and c++
– Definition of complex and user defined types- Encapsulation of operations and user defined methods Object oriented concept consists of
-abstract data types (class definition, provides extension to complex attribute types)
– Encapsulation (implementation of operations and objects structure hidden)
– Inheritance (sharing of data within hierarchy scope, supports code reusability)
-polymorphism (operator overloading)
The object oriented model provides useful tools for data abstraction and data structuring which gives the conventional tools and overcomes the deficiencies inherent to the traditional relational model. GIS integrate data from various resources into a single, homogeneous system, need powerful and flexible data models to serve tasks. The advantages of applying OO techniques to GIS system designs and application has been proven by previous OO approaches. Two main
merits of OO techniques are universally agreed:
-objects integrate graphic and attribute data as well as operations acting on those data and
– OO properties such as inheritance and class hierarchical structure simplify spatial data modeling..

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