History/Evolution of Database and History of Database Management System:
Due to the advancement in the electronic industry, the increased processing
power and storage capacity of computers have opened the doors for, computer
scientists to develop various techniques to store large amount of related data
in an efficient and compact manner. The concept of database was introduced by
IBM in 1960s. Since then, a lot of research has been done in this field. A brief
description about the development of DBMS and database models is given below:
Hierarchical DBMS:
A considerable research was conducted during 1960s. As a result, NAA (North
American Aviation) developed a software known as GUAM (Generalized Update Access
Method). GUAM was based on the concept that smaller components come together as
part of larger components and so on, until the final product is assembled. This
is like a hierarchical structure and thus known as hierarchical structure.
In the mid 1960s, IBM joined NAA to develop a system known as IMS (Information
Management System). IMS is still the main hierarchical DBMS used by most large
mainframe computers.
Network DBMS:
In the mid-1960s, another development was made known as IDS (Integrated Data
Store) by General Electric. This work was headed by Charles Bachman. This led to a new type of database system known as the
network DBMS. The network database system was developed partly to address the
need to represent more complex data relationships that could be modeled with
hierarchical structures, and partly to impose a database standard. To establish
such standards, the Conference on Data Systems Languages (CODASYL), comprising
representatives of the US Government and the world of business and commerce,
formed a List Processing Task Force in 1965. It was renamed as Data Base Task
Group (DBTG) in 1967. The terms of reference for the DBTG were to define
standard specifications for an environment that would allow database creation
and data manipulation. A draft report was issued in 1969 and the initial report
describing a network database implementation was issued in 1971. The DBTG
proposal identified three components:
- The network schema, which represents the logical organization of the entire
database as seen by the DBA. It includes the definition of the database name,
the type of each record, and the components of each record type.
- The subschema, which represents the part of the database as seen by the user
or application program.
- A Data Management Language, which is used to define the data structure, and to
manipulate the data etc.
For standardization, the DBTG specified three distinct languages:
- A schema Data Definition Language (DDL), which enables the DBA to . define the
schema.
- A subschema DDL, which allows the application programmers to define the parts
of the database they require.
- A Data Manipulation Language (DML), to manipulate the data of database.
Relational Database Systems:
In 1970, E. F. Codd of the IBM Research Laboratory published a paper on the
relational data model. In this paper he described a new system (i.e. relational
database model) for storing and working with large databases. He applied the
concepts of relational algebra (a branch of mathematics) to describe the new
system. Instead of records being stored in some sort of linked list of free-form
as in CODASYL, his concept was to use a "table" of fixed-length record', Many
experimental relational DBMSs were implemented thereafter, with the first
commercial products appearing in the late 1970s and early 1980s. IBM started
working on a prototype system based on Codd's concepts e.g., System R in the early
1970s.".This project led to two major developments:
(i) The development of a structured query language called SQL, which has since
become the standard language for relational systems.
(ii) The production of various commercial relational DBMS products were
introduced during the 1980s, For example, DB2 and SQL/DS from IBM and ORACLE
from ORACLE Corporation.
Now there are several hundred relational DBMSs for both mainframe and
microcomputer environments, though many are following the concept of the
relational model. Other examples of multi-user relational DBMS are INGRES from
Computer Associates, and INFORMIX from Informix Software Inc. and SYBASE from
Sybase Inc.
In 1979, dBase-It was developed by Ashton-Tate and it was called as relational
DBMS. It was very popular in PCs'. It was not a truly relational DBMS product.
In fact, it was a programming language with generalized file-processing
capabilities. After dBase, Foxpro was introduced. Actually, Foxpro was the
advanced version of dBase, but it was a truly relational DBMS product. Today the
most popular and commonly used PC-based truly relational DBMS products are
Oracle and Ms-Access.
Client-Server Database Applications:
Earlier multi-user architectures used mainframe computers to process the
database. The mainframe computer provides all the functions to the connected
users directly. The mainframe contains the DBMS software, application programs,
and user-interfaces. The users connected to the mainframe through their
terminals. The remote users were connected to mainframe in a communication network.
In the mid 1980s, most users began to share data through local area network
(LAN). The microcomputers were linked together in a LAN so that data and
resources such as printers, storage devices etc. could be shared. The LAN
enabled the users to send data to one another through computers. The first
application of LAN enabled the users to share the resources and to communicate
via electronic mail. The end-users also wanted to share their database, which
led to the development of multi-user database applications on LANs. After this,
the Client-Server architecture was introduced to share data on the computer
network.
Entity-Relationship Model:
The relational model also has limited modeling capabilities. In 1976, Peter Chen
presented the Entity-Relationship model for database design. The E-R data model
is a detailed, logical representation of the data for organization. The E-R
model is expressed in, terms of entities, relationships
between entities and the attributes (or properties) of both the entities and
their relationships. The E-R model is normally expressed as an E-R diagram,
which is a graphical representation of an E-R model.
Database Processing On Internet:
The Internet was introduced in 1969 by Advanced Research Projects Agency (ARPA)
of USA. Today, most of the database systems are online. It means that databases,
DBMS software and database applications are stored on the Web server, The
database technology is used in conjunction with Internet technology to access
data on the Web server. The database applications are developed using the
Internet technology to access the database on the Web server. The database on
the Internet uses the hypertext transfer protocol (HTTP), dynamic hypertext
markup language (DHTML), and extensible markup language (XML), to communicate
information between database application and database stored on the Web server..
Object Oriented Database Systems:
In the mid 1980s, it had become clear that there were several fields where
relational databases were not applicable, due to the types of data involved.
These included medicine, multimedia and high-energy physics, all of which needed
more flexibility in how their data was represented and accessed. This led to
research being started in object-oriented databases where users could define
their own methods of access to data and how it was represented and manipulated.
In the start of 1990s, two systems had appeared the Object-Oriented DBMS
(OODBMS) and the object-relational DBMS (ORDBMS). However, unlike previous
models, the actual composition of these models is not clear. This evolution
represents third generation DBMS.
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