Page 48 - DLIS408_INFORMATION_TECHNOLOGY-APPLICATIONSL SCIENCES

Unit 4: Database

No widely accepted exact definition exists for DBMS. However, a system needs to provide Notes
considerable functionality to qualify as a DBMS. Data collection needs to meet respective usability
requirements (broadly defined by the requirements below) to qualify as a database.

Did u know? The Oxford English dictionary cites a 1962 technical report as the first to use the
term “database.”

Self Assessment

Fill in the blanks:
1. An organized collection of data for one or more purposes, usually in digital form is called
.................... .
2. SQL stands for .................... .

4.2 Evolution of Database and DBMS Technology
The introduction of the term database coincided with the availability of directaccess storage (disks
and drums) from the mid-1960s onwards. The term represented a contrast with the tape-based
systems of the past, allowing shared interactive use rather than daily batch processing.

In the earliest database systems, efficiency was perhaps the primary concern, but it was already
recognized that there were other important objectives. One of the key aims was to make the data
independent of the logic of application programmes, so that the same data could be made available
to different applications.
The first generation of database systems were navigational and pointers from one record to
another. The two main data models at this time were the hierarchic model, epitomized by IBM’s
IMS system and the Codasyl model (Network model, implemented in a number of products such
as IDMS.
The Relational model was first proposed in 1970. Later it was insisted that applications should search
for data by content, rather than by following links. This was considered necessary to allow the
content of the database to evolve without constant rewriting of applications. Relational systems
placed heavy demands on processing resources, and it was not until the mid 1980s that computing
hardware became powerful enough to allow them to be widely deployed. By the early 1990s, however,
relational systems were dominant for all large-scale data processing applications, and they remain
dominant today (2011) except in niche areas. The dominant database language is the standard SQL for
the Relational model, which has influenced database languages also for other data models.
As the relational model emphasizes search rather than navigation, it does not make relationships
between different entities explicit in the form of pointers, but it represents using primary keys and
foreign keys. While this is a good basis for a query language, it is less well suited as a modeling
language. For this reason a different model, the Entity-relationship model which emerged shortly
later (1976), gained popularity for database design.
During 1970s, database technology has kept pace with the increasing resources becoming available
from the computing platform: notably the rapid increase in the capacity and speed (and reduction
in price) of disk storage, and the increasing capacity of main memory.

Notes The rigidity of the relational model has a limitation in handling information that is
richer or more varied in structure than the traditional ‘ledger-book’ data of corporate
information systems.

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