Saturday, 9 March 2013

Define the following terms. i. Database ii. Database Management System iii. Data Model iv. Schema v. Data Independence

Database:

A collection of related information stored in a structured format. Database is often used interchangeably with the term table (Lotus Approach, for instance, uses the term database instead of table). Technically, they're different: A table is a single store of related information; a database can consist of one or more tables of information that are related in some way. For instance, you could track all the information about the students in a school in a students table. If you then created separate tables containing details about teachers, classes and classrooms, you could combine all four tables into a timetabling database. Such a multi-table database is called a relational database..


Database Management System:

A Database Management System is a collection of interrelated data and a set of programs to access that data. The primary goal of a DBMS is to provide a way to store and retrieve database information that is both convenient and efficient.

Data Model:
Data modeling is the analysis of data objects that are used in a business or other context and the identification of the relationships among these data objects. Data modeling is a first step in doing object-oriented programming. As a result of data modeling, you can then define the classes that provide the templates for program objects.
Schema:

The collection of information stored in the database at a particular moment is called an instance of the database. The overall design of the database is called the database schema. Schemas are changed infrequently.  Database systems have several schemas, partitioned according to the levels of abstraction. The physical schema, logical schema and subschema.
Data Independence:
Data independence occurs when the structure of the database can change without requiring programs that access the database to change. Data independence is achieved through the use of the view. Each program accesses data through an external view. The underlying structure of the database can change without requiring a change in the external view. The change to the database structure should be such that a required field should not be removed from the database structure.