Type of Database Models

Type of Database Models

Database management systems were first introduced during the 1960s and have continued to evolve during subsequent decades. Some combinations of the fallowing three objectives always drove the development and evolution of database technology.

• To provide greater independence between programs and data
• To manage increasingly complex data types and structures
• To provide easier and faster access to data for non-computer professional

Hierarchical and network database model

The hierarchical and network database management systems (generally regarded as first-generation DBMS) were developed to cope with increasingly complex data structures. Both approach to database structure used physical pointers, or disk addresses, to relate records in different files.

Hierarchical Database Model	Network Database Model
Organized as a family tree structure (simple)	Organized as network structure (complex)
One to many relationship (parent Child)	Many to many relationship
Top most record is the root record	Many records at top level
Whole database depends on root record	Database does not depends on a root record
Data access using pointers	Data access using pointers
Access using navigational records at a time procedure	Access using navigational records at a time procedure
Single access path for a data record	Multiple access paths for a data record
Data record can be duplicated	Data records are not duplicated
Need to write complex quires to get information from multiple branches. (no cross links)	Can write simple quires to get information from multiple branches because cross link available

The Hierarchical database model was developed to overcome the limitation of file processing systems and network model has derived as a solution to problem caused by hierarchical model. And both have following problems.

• Difficult access to data based on navigational records at-a-time procedures.
• Very limited data independence
• No widely accepted theoretical foundation for either model