Network Model in DBMS

Structure of a Network Model

The structure of a network model is based on the concept of a directed graph. In this structure, records are represented as nodes, & the relationships between them are represented as edges or links. Each record can have multiple parent & child records, creating a complex network of connections.

The network model consists of three main components:

1. Records: These are the basic building blocks of the database & contain the actual data. Each record is made up of fields, which are the individual pieces of data that make up the record.
 

2. Sets: Sets define the relationships between records. Each set consists of an owner record & a member record, & the connection between them is called a link. Sets can be one-to-one, one-to-many, or many-to-many.

3. Links: Links are the connections between records in a set. They define the relationship between the owner record & the member record. Links are bidirectional, which means that they can be traversed in both directions.

The structure of a network model allows for the creation of complex networks of data that can be traversed in multiple ways. This makes it possible to retrieve data based on multiple criteria & to navigate through the database using different paths.

Example

Let's consider an example of a university database that uses the network model. In this database, we have three main record types: students, courses, & instructors.

The relationships between these record types can be defined using sets. For example, we can have a set called "Enrollment" that connects students to the courses they are enrolled in. The owner record in this set would be the student record, & the member record would be the course record. Each student can be enrolled in multiple courses, & each course can have multiple students enrolled in it.

We can also have a set called "Teaching" that connects instructors to the courses they teach. The owner record in this set would be the instructor record, & the member record would be the course record. Each instructor can teach multiple courses, & each course can be taught by multiple instructors.

Using these sets & links, we can create a network of connections between students, courses, & instructors. We can traverse this network in multiple ways to retrieve data based on different criteria. For example, we can find all the courses a particular student is enrolled in, or we can find all the students enrolled in a particular course taught by a specific instructor.

Advantages of Network Model

The network model has several advantages over other database models, such as the hierarchical model. Some of the main advantages are:

1. Flexibility: The network model allows for the creation of complex relationships between records, which makes it more flexible than the hierarchical model. It can handle many-to-many relationships, which are not possible in the hierarchical model.

2. Efficiency: The network model is more efficient than the hierarchical model when it comes to retrieving data. Because it allows for multiple access paths to the same data, it can retrieve data more quickly & with fewer disk accesses.

3. Data Integrity: The network model enforces data integrity through the use of sets & links. This ensures that the relationships between records are always maintained & that data is not lost or corrupted.

4. Improved Data Modeling: The network model allows for more accurate modeling of real-world relationships between data. It can handle complex relationships that are not possible in other models, such as the hierarchical model.

5. Reduced Data Redundancy: The network model reduces data redundancy by allowing data to be stored in a single location & accessed through multiple paths. This reduces the need for duplicate data & saves storage space.

Disadvantages of the Network Model

Just like every other technology, this also has it’s disadvantages also. Some of the main disadvantages are:

1. Complexity: The network model can be complex to design & implement, especially for large databases with many record types & relationships. This complexity can make it difficult to maintain & modify the database over time.

2. Lack of Standards: Unlike other database models, such as the relational model, the network model lacks a standard language for defining & manipulating data. This can make it difficult to port a network database to another system or to integrate it with other applications.

3. Limited Query Flexibility: While the network model allows for multiple access paths to data, it can be less flexible than other models when it comes to querying data. Complex queries may require navigating through multiple sets & links, which can be time-consuming & error-prone.

4. Navigational Complexity: Navigating through a network database can be complex, especially for users who are not familiar with the database structure. This can make it difficult for users to find the data they need & can lead to errors & inconsistencies in data entry.

5. Lack of Independence Between Programs & Data: In the network model, the structure of the database is closely tied to the programs that access it. This can make it difficult to modify the database structure without also modifying the programs that use it.

Features of Network Model in DBMS

The network model in DBMS has several key features that distinguish it from other database models. The main features are:

1. Many-to-Many Relationships: The network model allows for the creation of many-to-many relationships between records. This means that a single record can have multiple parent records & multiple child records, creating a complex network of connections.

2. Ownership & Membership: In the network model, relationships between records are defined using sets. Each set consists of an owner record & a member record, & the connection between them is called a link. The owner record controls access to the member record & is responsible for maintaining the integrity of the relationship.

3. Navigational Access: The network model provides navigational access to data, which means that users can traverse the network of connections between records to find the data they need. This is done using a language called the Data Manipulation Language (DML), which allows users to specify the path they want to follow through the database.

4. Efficient Data Retrieval: Because the network model allows for multiple access paths to the same data, it can retrieve data more efficiently than other models. This is particularly true for databases with complex relationships between records, where the ability to navigate through the network can significantly reduce the number of disk accesses required to retrieve data.

5. Data Integrity: The network model enforces data integrity through the use of sets & links. This ensures that the relationships between records are always maintained & that data is not lost or corrupted.

6. Flexibility: The network model is highly flexible & can be adapted to a wide range of database applications. It can handle complex relationships between records & can be used to model real-world systems in a way that is intuitive & easy to understand.

Operations on Network Model in DBMS

The network model in DBMS supports several basic operations that allow users to manipulate & retrieve data from the database. The main operations are:

1. Insertion

Insertion is the process of adding new records to the database. In the network model, insertion involves creating a new record & linking it to existing records using sets. The new record becomes the owner or member record in one or more sets, depending on its relationship to other records in the database.

2. Deletion

Deletion is the process of removing records from the database. In the network model, deletion involves unlinking a record from its owner & member records in all sets that it participates in, & then removing the record itself from the database. It is important to ensure that all links to the deleted record are removed to maintain the integrity of the database.

3. Modification

Modification is the process of changing the values of fields in a record. In the network model, modification involves navigating to the record that needs to be modified, making the necessary changes, & then saving the modified record back to the database.

4. Retrieval

Retrieval is the process of accessing & displaying data from the database. In the network model, retrieval involves navigating through the network of connections between records to find the desired data. This is typically done using a query language, such as the Data Manipulation Language (DML), which allows users to specify the path they want to follow through the database.

5. Traversal

Traversal is the process of navigating through the network of connections between records in the database. In the network model, traversal involves following the links between owner & member records in sets to access related data. Traversal can be done in a forward or backward direction, depending on the specific needs of the application.

Difference Between the Network Model and the Hierarchical Model

Frequently Asked Questions

Is the network model still used today?

While the network model is not as widely used as the relational model, it is still used in some legacy systems & specialized applications where its unique features are beneficial.

Can the network model handle many-to-many relationships?

Yes, the network model is designed to handle many-to-many relationships between records, which is one of its main advantages over the hierarchical model.

Is it easy to modify the structure of a network database?

Modifying the structure of a network database can be complex, as changes to the schema may require modifications to the application programs that access the database.

Conclusion

In this article, we have talked about the network model in database management systems. We have learned about its structure, which is based on records, sets, & links, & how it allows for the creation of complex, many-to-many relationships between records. We have also explained its advantages, such as flexibility & efficiency, as well as its disadvantages, like complexity & lack of standards. Additionally, we have discussed the key features & operations of the network model & compared it to the hierarchical model. 

You can also practice coding questions commonly asked in interviews on Coding Ninjas Code360. 

Also, check out some of the Guided Paths on topics such as Data Structure and Algorithms, Competitive Programming, Operating Systems, Computer Networks, DBMS, System Design, etc., as well as some Contests, Test Series, and Interview Experiences curated by top Industry Experts.