Network Model in DBMS – Scaler Topics

Overview

A database model is the logical representation of the database i.e. the constraints and the relationship between the stored data. The Network Model in DBMS is a hierarchical model that is used to represent the many-to-many relationship among the database constraints. It is represented in the form of a graph hence it is a simple and easy-to-construct database model. The network model in DBMS allows 1 : 1 (one-to-one), 1 : M (many-to-one), M : N (many-to-one) relationships among the entities or members. Click here, to know more about relationships in DBMS.

Scope of the Article

The article covers topics such as

• Introduction to the Network Model in DBMS.
• The structure of the Network Model in DBMS.
• Characteristics of the Network Model in DBMS.
• Examples of the Network Model in DBMS and Network databases.
• Operations on the Network Model in DBMS.
• Advantages and Disadvantages of the Network Model in DBMS.
• Difference between the Network model, Hierarchical model, and Relational model.

Each of the topics is explained clearly with diagrams and examples wherever necessary.

Introduction to Network Model in DBMS

DBMS stands for Data Base Management System. DBMS is computer software that is used to arrange, manage, and manipulate databases. DBMS provides an interface to perform the operations like data creation, updating data creating a table in the database, and a lot more.

A database model is the logical representation of the database i.e. the constraints and the relationship between the stored data. The database model is usually represented in the form of flow diagrams called database diagram. There are various types of database models such as:

• Relational model
• Hierarchical model
• Network model
• Object-oriented database model
• Object-relational model
• Entity-relationship model
• Other database models
• NoSQL database models
• Databases on the Web

Now, the Network Model in DBMS is a hierarchical model that is used to represent the many-to-many relationship among the database constraints. It is a simple and easy-to-construct database model. The Network Model in DBMS is based on the set theory (mathematical set theory), so the model of the database is constructed with the set of related records (data).

The Network Model in DBMS was one of the most popular models before the introduction of the relational model as it is easy to create and visualize. It is represented in the form of a graph. Let us take an example of a simple College database that has two departments or sections namely – the CSE Department and the Library. All the students of the college can go to both the departments. So, let us try to represent this hierarchal relationship (Refer to the diagram below for better visualization).

In the example above, the Student entity has two parents namely – CSE Department and Library. The CSE Department and Library have the same parent College

Note: The network model in DBMS was formalized by the Database Task group in the 1960s.

Structure of a Network Model in DBMS

Although the network model in DBMS is a hierarchal structure but is different from the hierarchal database model as there can be numerous parents of a member.

Let us take a basic hierarchal structure to visualize the structure of a network model in DBMS.

The above structure represents a network model in which ONE is the prime owner of the model (in simple terms we can say that the rest of the members are dependent on ONE). Similar to that, member FIVE has two owners namely – TWO and THREE. The network database model allows 1 : 1 (one-to-one), 1 : M (many-to-one), M : N (many-to-one) relationships among the entities or members. The modeled hierarchal structure helps in avoiding data redundancy problems as there are multiple paths to the same record.

Refer to the Examples of Network Model in DBMS section for a better understanding of a real-life example.

Characteristics of Network Model

Let us discuss the various characteristics of the network database model.

• The network model in DBMS is better than the hierarchical model as there are more interrelations between entities.
• Supports various relationships such as one-to-one, one-to-many, and many-to-many as well.
• An entity can have various parents or owners.
• The connected structure results in high performance.
• All the entities are interconnected with each other as a connected network.
• The connected network of the database entities is represented in the form of a graph for better representation, workflow, and visualization.
• The network model in DBMS is not very flexible.
• It is also quite a complex structure to deal with.
• There can be more than one path to a certain record in DBMS which makes the data retrieval faster and simple.
• The operations performed in the network database model using a circular linked list (Refer to the

  Operations on Network Model in DBMS

  section for more details).

• The Network Model in DBMS does not support the query facility.
• The 3GL programs are used by programmers to represent the relationship among the various entities of the Network Model in DBMS.

Examples of Network Model in DBMS

Let us take a basic example to visualize the structure of a network model in DBMS.

Suppose we are designing the network model for the Students database. As we can see that the Subject entity has a relationship with both the Student entity and Degree entity. So there is an edge connecting the Subject entity with both Student and Degree.

The Subject entity has two parents and the other two entities have one child entity.

Other examples of the network model in DBMS can be:-

• Store database (having relation between customers, manager, salesman, order, items, etc.).
• Finance Department database (having relation between customers, products, invoices, payments, etc.).

Examples of Network Databases

Some of the famous network databases can be:-

• TurboIMAGE
• Integrated Data Store (IDS)
• Raima Database Manager
• Univac DMS-1100
• IDMS (Integrated Database Management System), etc.

Operations on Network Model in DBMS

Let us discuss the various operation that can be performed on the Network Model in DBMS.

• Insertion Operation – We can insert or add a new record in the network database model but before adding any new record the database administrator or the user needs to understand the whole structure.

• Update Operation – We can update the data record(s). If a certain data is updated then all its children entities are also affected.

• Deletion Operation – We can delete the data record(s) but the deletion is a very crucial operation. Before deleting any record, we should first look out for the various connected entities so that the corresponding entities do not get affected by the deletion.

• Retrieval Operation – The retrieval of records in the network model in DBMS is quite complex to program but it is very fast as the entities are interconnected and various paths lead to certain records.

Advantages of Network Model in DBMS

Let us now discuss some of the advantages of the Network Model in DBMS:

• It is a simple and easy-to-construct hierarchical database model.
• The network model in DBMS allows 1 : 1 (one-to-one), 1 : M (many-to-one), M : N (many-to-one) relationships among the entities or members.
• In the network model in DBMS, there are multiple paths to the same record which helps in avoiding data redundancy problems.
• In the network model in DBMS, there is data integrity as every member entity has one or more owners. Only the prime parent has no owner but it has various inter-related children.
• The data retrieval is faster in the case of the network model in DBMS because the entities and the data are more interrelated.
• Due to the parent-child relationship, if there is a change in the parent entity, it is reflected in the children’s entity as well. It also saves time as we do not need to update all the related children entities.

Disadvantages of Network Model in DBMS

Let us now discuss some of the disadvantages of the Network Model in DBMS:

• The network database model is very complicated due to several entities inter-related with each other. So, managing is also quite difficult.
• In the case of the addition of new entities, the database administrator or the user needs to understand the whole structure.
• Due to complex inter-related structure the addition, update, as well as deletion are very difficult.
• There is no scope for any automated query optimization in DBMS.
• We need to use a pointer for navigation hence the operational anomalies exist.

Network model VS Hierarchical Model VS Relational Model

As we have seen the Network model, Hierarchical model, and Relational model are somewhat related to each other. Let us now discuss the difference between them.

Network Data ModelHierarchical Data ModelRelational Data ModelIn the Network data model, we use links to represent the relation among the various entities.In the Hierarchical data model, the representation is done in the form of the parent-child relationship.In the Relational data model, we use keys to represent the relationship between the records.The relation among the entities can be in the form of a many-to-many relationship.The relation among the entities cannot be in the form of a many-to-many relationship.The relation among the entities can be in the form of the many-to-many relationship more easily.There is no problem with data inconsistency.There is a chance of data inconsistency in case of data updation and deletion.It maintains the data integrity and consistency by using the normalization technique.The relationship among the records is quite complex due to the usage of pointers.There are various methods to implement the relationship among entities such as simple, natural, and straightforward.We use keys (such as primary keys, foreign keys, composite keys, etc.) to represent the relationship among the various entities.The searching for a record is very easy as there are numerous paths to a certain record.The searching for a record is very difficult as a child’s record can only be found after going through the parent’s record.We use a unique key (identifier key) to search for the record(s).It is very useful to represent the records that have a many-to-many relationship.It is very useful in the cases where there is some hierarchical relationship among the entities.It is very useful to represent real-world objects and the relationship among the various objects.

Conclusion

• A database model is the logical representation of the database i.e. the constraints and the relationship between the stored data.
• Network Model in DBMS is a hierarchical model that is used to represent the many-to-many relationship among the database constraints.
• The network model in DBMS is a hierarchal structure but is different from the hierarchal database model as there can be numerous parents of a member.
• The network model in DBMS allows 1 : 1 (one-to-one), 1 : M (many-to-one), M : N (many-to-one) relationships among the entities or members.
• In the network model in DBMS, there are multiple paths to the same record which helps in avoiding data redundancy problems.
• In the network model in DBMS, there is data integrity as every member entity has one or more owners. Only the prime parent has no owner but it has various inter-related children.
• The network database model is very complicated due to several entities inter-related with each other. So, managing is also quite difficult.