Evolution of Database Management Systems

A database management system (DBMS) consists of collection of interrelated data and a set of programs to access that data. It is software that is helpful in maintaining and utilizing a database.

The chronological order of the development of DBMS is as follows:

– Flat files – 1960s–1980s
– Hierarchical – 1970s–1990s
– Network – 1970s–1990s
– Relational – 1980s–present
– Object-oriented – 1990s–present
– Object-relational – 1990s–present
– Data warehousing – 1980s–present
– Web-enabled – 1990s–present

• Early 1960s. Charles Bachman at GE created the first general purpose DBMS Integrated Data Store. It created the basis for the network model which was standardized by CODASYL (Conference on Data System Language).
• Late 1960s. IBM developed the Information Management System (IMS). IMS used an alternate model, called the Hierarchical Data Model.
   
• 1970. Edgar Codd, from IBM created the Relational Data Model. In 1981 Codd received the Turing Award for his contributions to database theory. Codd Passed away in April 2003.
• 1976. Peter Chen presented Entity-Relationship model, which is widely used in database design.
• 1980. SQL developed by IBM, became the standard query language for databases. SQL was standardized by ISO.
• 1980s and 1990s. IBM, Oracle, Informix and others developed powerful DBMS.

In a database, the information is stored in a tabular form where data may or may not be interlinked. Hence we can say that basically database is a compilation of database files and each database file is further a collection of records.

Flat files (1960s – 1980s)

Flat file database is a database that stores information in a single file or table. In a text file, every line contains one record where fields either have fixed length or they are separated by commas, whitespaces, tabs or any other character. In a flat file database, there is no structural relationship among the records and they cannot contain multiple tables as well.

Hierarchical database (1970s – 1990s)

As the name indicates, hierarchical database contains data in a hierarchically-arranged data. More perceptively it can be visualized as a family tree where there is a parent and a child relationship. Each parent can have many children but one child can only have one parent i.e.; one-to-many relationship. Its hierarchical structure contains levels or segments which are equivalent to the file system’s record type. All attributes of a specific record are listed under the entity type.

In hierarchical database, the entity type is the main table, rows of a table represent the records and columns represent the attributes.

Network database (1970s – 1990s)

The inventor of network model is Charles Bachmann. Unlike hierarchical database model, network database allows multiple parent and child relationships i.e., it maintains many-to-many relationship. Network database is basically a graph structure. The network database model was created to achieve three main objectives:

1. To represent complex data relationships more effectively.
2. To improve the performance of the database.
3. To implement a database standard.

In a network database a relationship is referred to as a set. Each set comprises of two types of records, an owner record which is same as parent type in hierarchical and a member record which is similar to the child type record in hierarchical database model.

Relational database (1980s – present)

Relational database model was proposed by E.F. Codd. After the hierarchical and network model, the birth of this model was huge step ahead. It allows the entities to be related through a common attribute. So in order to relate two tables (entities), they simply need to have a common attribute. In the tables there are primary keys and alternative keys. Primary keys form a relation with the alternative keys. This property makes this model extremely flexible.

Thus using relational database ample information can be stored using small tables. The accessing of data is also very efficient. The user only has to enter a query, and the application provides the user with the asked information.

Relational databases are established using a computer language, Structured Query Language (SQL). This language forms the basis of all the database applications available today, from Access to Oracle.

Object-oriented database (1990s – present)

Object oriented database management system is that database system in which the data or information is presented in the form of objects, much like in object-oriented programming language. Furthermore, object oriented DBMS also facilitate the user by offering transaction support, language for various queries, and indexing options. Also, these database systems have the ability to handle data efficiently over multiple servers.

Unlike relational database, object-oriented database works in the framework of real programming languages like JAVA or C++.

Object-relational database (1990s – present)

Defined in simple terms, an object relational database management system displays a modified object-oriented user-display over the already implemented relational database management system. When various software interact with this modified-database management system, they will customarily operate in a manner such that the data is assumed to be saved as objects.

The basic working of this database management system is that it translates the useful data into organized tables, distributed in rows and columns, and from then onwards, it manages data the same way as done in a relational database system. Similarly, when the data is to be accessed by the user, it is again translated from processed to complex form.

Web enabled database (1990s – present)

• Web enabled database simply put a database with a web-based interface.
• This implies that there can be a separation of concerns; namely, the web designer does
• not need to know the details about the DB’s underlying design. Similarly, the DB designer needs to concern himself with the DB’s web interface.
• A web enabled database uses three layers to function: a presentation layer, a middle layer and the database layer

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