Database Management System
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In this section we discuss in an informal manner the idea of a database as an abstract
machine. An abstract machine is a model of the key features of some system without
any details of implementation. The objective of this section is to describe the
fundamental concepts of a database system without introducing any formal notation, or
introducing any concepts of representation, development or implementation.
What is a Database?
Most modern-day organizations have a need to store data relevant to their day today
activities. Those organizations choose an electronic database to organize and store
some of this data.
Take for instance a university. Most universities need to record data to help in the
activities of teaching and learning. Most universities need to record, among other things:
· What students and lecturers they have
· What courses and modules they are running
· Which lecturers are teaching which modules
· Which students are taking which modules
· Which lecturer is assessing against which module
· Which students have been assessed in which modules
Various members of staff at a university will be entering data such as this into a
database system. For instance, administrators in academic departments may enter data
relevant to courses and modules, course co-coordinators may enter data pertaining to
lecturers, and data relevant to students, particularly their enrolments on courses and
modules, may be entered by staff at a central registry.
Once the data is entered into the database it may be utilized in a variety of ways. For
example, a complete and accurate list of enrolled students may be used to generate
membership records for the learning resources center; it may be used as a claim to
educational authorities for student income or as an input into a timetabling system which
might attempt to optimize room utilization across a university campus.
Properties of a Database
The term database also usually implies a series of related properties: data sharing, data
integration, data integrity, data security, data abstraction and data independence.
Data stored in a database is not usually held solely for the use of one person. A
database is normally expected to be accessible by more than one person, perhaps at
the same time. Hence a students' database might be accessible by members of not only
academic but also administrative staff.
Shared data brings numerous advantages to the organization. Such advantages,
however, only result if the database is treated responsibly. One major responsibility of
database usage is to ensure that the data is integrated. This implies that a database
should be a collection of data, which, at least ideally, has no redundant data. Redundant
data is unnecessarily duplicated data.
In the past, for instance separate files of student information might have been
maintained by different academic and administrative departments of a university with
many Fields in common. The aim of a database system would be to store one logical
item of data in one place only. Hence, one student record would be accessible to a
range of information systems.
Another responsibility arising as a consequence of shared data is that a database should
display integrity. In other words, that the database should accurately reflect the universe
of discourse that it is attempting to model.