February 01, 2020
Amitraj
Network Model
This is an extension of the Hierarchical model. In this model data is organised more like a graph, and are allowed to have more than one parent node.
In this database model data is more related as more relationships are established in this database model. Also, as the data is more related, hence accessing the data is also easier and fast. This database model was used to map many-to-many data relationships.
This was the most widely used database model, before Relational Model was introduced.
OR
The Network model is a flexible way of representing entities and their relationships. This model form a graph in which entities are nodes and relationship types are connecting edges.
-> Here one entity can be related to multiple other entities. Relationship cycles are also permitted.
Advantages Of Network Model -
1. Ease of data access- The data access is easier and flexible than the hierarchical model.
2. Data integrity- The network model does not allow a member to exist without an owner.
4. Conceptual simplicity - Just like the hierarchical model,the network model is also conceptually simple and easy to design.
5. Capability to handle more relationship types - The network model can handle the one to many and many to many relationships which is real help in modeling the real life situations.
Disadvantages Of Network Model -
1. Absence of structural independence- structural changes to the database is very difficult.
2. System complexity- All the records are maintained using pointers and hence the whole database structure becomes very complex.
3. Operational Anomalies- The insertion,deletion and updating operations of any record require large number of pointers adjustments.
Data-Structure Diagrams
-> Schema representing the design of a network database.
-> A data-structure diagram consists of two basic components -
Boxes, which correspond to record types.
Lines, which correspond to links.
-> Specifies the overall logical structure of the database.
-> For every E-R diagram, there is a corresponding data-structure
diagram.
-> Since a link can not contain any data value, represent an E-R
relationship with attributes with a new record type and links.
This is an extension of the Hierarchical model. In this model data is organised more like a graph, and are allowed to have more than one parent node.
In this database model data is more related as more relationships are established in this database model. Also, as the data is more related, hence accessing the data is also easier and fast. This database model was used to map many-to-many data relationships.
This was the most widely used database model, before Relational Model was introduced.
OR
The Network model is a flexible way of representing entities and their relationships. This model form a graph in which entities are nodes and relationship types are connecting edges.
-> Here one entity can be related to multiple other entities. Relationship cycles are also permitted.
Advantages Of Network Model -
1. Ease of data access- The data access is easier and flexible than the hierarchical model.
2. Data integrity- The network model does not allow a member to exist without an owner.
4. Conceptual simplicity - Just like the hierarchical model,the network model is also conceptually simple and easy to design.
5. Capability to handle more relationship types - The network model can handle the one to many and many to many relationships which is real help in modeling the real life situations.
Disadvantages Of Network Model -
1. Absence of structural independence- structural changes to the database is very difficult.
2. System complexity- All the records are maintained using pointers and hence the whole database structure becomes very complex.
3. Operational Anomalies- The insertion,deletion and updating operations of any record require large number of pointers adjustments.
Data-Structure Diagrams
-> Schema representing the design of a network database.
-> A data-structure diagram consists of two basic components -
Boxes, which correspond to record types.
Lines, which correspond to links.
-> Specifies the overall logical structure of the database.
-> For every E-R diagram, there is a corresponding data-structure
diagram.
-> Since a link can not contain any data value, represent an E-R
relationship with attributes with a new record type and links.
