Evolution of Data Models
The Evolution of Data Models
The quest for better data management has led to different models that attempt to resolve the file system’s critical shortcomings. Because each data model evolved from its predecessors, it is essential to examine the major data models in roughly chronological order.
1.1 The Hierarchical Model
A Hierarchical Database Model is a data model in which the data is organized into a tree-like structure. The structure allows representing information using parent/child relationships: each parent can have many children, but each child has only parent. All attributes of a specific record are listed under an entity type.
Example of a hierarchical model
In a database an entity type is the equivalent of a table. Each individual record is represented as a row, and each attribute as a column. Entity types are related to each other using 1:N mappings, also known as one-to-many relationship. This model is recognized as the first database model created by IBM in the 1960’s.
Currently the most widely used hierarchical database are IMS developed by IBM and Windows Registry by Microsoft
Advantages 1. Conceptual simplicity 2. Database security 3. Data independence (because the data characteristics of the database structure are not defined in the programs accessing the database, instead the database structure and its data characteristics are defined in the data dictionary component of the DBMS. Therefore the programs accessing the database become independent of the database) 4. Database integrity (because data duplication or data redundancy is minimized as a result of relating the segments or records) 5. Efficiency (the hierarchical DBMS file storage organization and access methods are based on the new hierarchal database structure which is much faster than the file storage organization and access methods used in the old file system)
Disadvantages 1. Complex implementation 2. Difficult to manage 3. Lacks
The quest for better data management has led to different models that attempt to resolve the file system’s critical shortcomings. Because each data model evolved from its predecessors, it is essential to examine the major data models in roughly chronological order.
1.1 The Hierarchical Model
A Hierarchical Database Model is a data model in which the data is organized into a tree-like structure. The structure allows representing information using parent/child relationships: each parent can have many children, but each child has only parent. All attributes of a specific record are listed under an entity type.
Example of a hierarchical model
In a database an entity type is the equivalent of a table. Each individual record is represented as a row, and each attribute as a column. Entity types are related to each other using 1:N mappings, also known as one-to-many relationship. This model is recognized as the first database model created by IBM in the 1960’s.
Currently the most widely used hierarchical database are IMS developed by IBM and Windows Registry by Microsoft
Advantages 1. Conceptual simplicity 2. Database security 3. Data independence (because the data characteristics of the database structure are not defined in the programs accessing the database, instead the database structure and its data characteristics are defined in the data dictionary component of the DBMS. Therefore the programs accessing the database become independent of the database) 4. Database integrity (because data duplication or data redundancy is minimized as a result of relating the segments or records) 5. Efficiency (the hierarchical DBMS file storage organization and access methods are based on the new hierarchal database structure which is much faster than the file storage organization and access methods used in the old file system)
Disadvantages 1. Complex implementation 2. Difficult to manage 3. Lacks