Page 180 - DCAP312_WEB_TECHNOLOGIES_II

Web Technologies-II

Notes Objectives

After studying this unit, you will be able to:

• Describe the concept of database model
• Discuss the hierarchical database model
• Explain the network database model
• Understand the relational database model

• Define the types of databases
• Explain that how create a basic object model

• Describe the creating the user interface
Introduction

We have the benefit of database systems and established how they are superior to the earlier file
oriented data systems. We caught a glimpse of the features of database systems that produce
several benefits. Database systems reduce data redundancy, integrate corporate data, and enable
information sharing among the various groups in the organization. Now you are ready for an
initial, formal definition of a database.
A data model represents the data requirements of an organization. You can diagrammatically
show a data model with symbols and figures. Data for an organization reside in a database.
Therefore, when designing a database, you first create a data model. The model would represent
the real-world data requirements. It would show the arrangement of the data structures.

Database software has evolved to support different types of data models. As we try to represent
real-world data requirements as close as possible in a data model, we come up with a replica
of the real-world information requirements. It turns out that we can look at data requirements
and create data models in a few different ways. At this stage, let us survey a few leading data
models. Over time, different vendors have developed commercial database management systems
to support each of these common data models.
Let us examine the following definition:
A database is an ordered collection of related data elements intended to meet the information
needs of an organization and designed to be shared by multiple users.
The key terms in the definition:
Ordered Collection: A database is a collection of data elements. Not just a random assembly of
data structures, but a collection of data elements put together deliberately with proper order.
The various data elements are linked together in the most logical manner.
Related Data Elements: The data elements in a database are not disjointed structures without
any relationships among them. These are related among themselves and also pertinent to the
particular organization.
Information Needs: The collection of data elements in a database is there for a specific purpose.
That purpose is to satisfy and meet the information needs of the organization. In a database
for a bank, you will find data elements that are pertinent to the bank’s business. You will find
customer’s bank balances and ATM transactions. You will not find data elements relating to a
student’s major and examination grades that belong in a database for a university. You will not
find a patient’s medical history that really belongs in a database for a medical centre.

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