1. Introduction to the Network Model
The Network Model is an extension of the Hierarchical Model, designed to handle many-to-many relationships efficiently. It was developed in the 1960s as part of the CODASYL (Conference on Data Systems Languages) DBTG (Database Task Group).
Key Features of the Network Model
✅ Records (Nodes) and Links (Edges) → Data is stored as records, connected via links (pointers).
✅ Many-to-Many Relationships → Unlike the Hierarchical Model, each child can have multiple parents.
✅ Flexible Data Representation → More efficient than the hierarchical model for complex relationships.
✅ Data Access Through Pointers → Uses navigational access via pre-defined links between records.
2. Structure of the Network Model
In the Network Model, data is represented using:
- Records (Nodes): Represent entities (e.g., Students, Courses).
- Links (Edges): Define relationships between records using pointers.
Example: Student-Course Relationship
| Student_ID | Student_Name |
|---|---|
| 101 | Alice |
| 102 | Bob |
| Course_ID | Course_Name |
|---|---|
| C1 | Database |
| C2 | Networking |
🔹 A student can enroll in multiple courses.
🔹 A course can have multiple students.
Graph Representation of the Network Model
(Alice) ----> (Database)
| |
v v
(Bob) ----> (Networking)
Here:
- “Alice” is linked to both “Database” and “Networking”.
- “Bob” is also linked to both “Database” and “Networking”.
- Many-to-Many relationships are possible.
3. How the Network Model Works
Data Storage & Access
- Data is stored in records, and relationships are maintained using pointers.
- To retrieve a record, the system follows pointers (links) instead of searching the entire database.
Example: Bank Database
Customer -----> Account
| |
v v
Loan <----> Branch
In a banking system:
- A Customer can have multiple accounts and loans.
- A Branch can offer multiple loans and handle multiple accounts.
- This complex relationship is efficiently handled by the Network Model.
4. Advantages of the Network Model
✅ 1. Supports Many-to-Many Relationships
- Unlike the Hierarchical Model, the Network Model allows flexible relationships.
✅ 2. Faster Data Access
- Uses pointers for retrieval, making searches faster compared to relational models.
✅ 3. More Efficient than Hierarchical Model
- No need to duplicate data when an entity has multiple parent relationships.
✅ 4. Reduces Data Redundancy
- Since multiple relationships are supported, data duplication is minimized.
5. Disadvantages of the Network Model
❌ 1. Complex Implementation
- The pointer-based structure makes it hard to modify or update relationships.
❌ 2. Complex Query Processing
- Queries require navigating through multiple pointers, making ad hoc queries difficult.
- Unlike SQL in the Relational Model, the Network Model requires navigational commands.
❌ 3. Difficult Database Design
- Relationships must be predefined before storing data, reducing flexibility.
6. Applications of the Network Model
Even though relational databases (RDBMS) are dominant today, the Network Model is still used in certain applications:
1. Banking Systems
- Customer-Account-Branch relationships where multiple customers can have multiple accounts.
2. Telecom Networks
- Managing connections between cell towers, customers, and data services.
3. Airline Reservation Systems
- A passenger can book multiple flights, and a flight can have multiple passengers.
4. Supply Chain Management
- Manufacturers, suppliers, and retailers form complex relationships that need a network model.
7. Comparison: Network vs. Other Models
| Feature | Hierarchical Model | Network Model | Relational Model |
|---|---|---|---|
| Structure | Tree (One-to-Many) | Graph (Many-to-Many) | Tables (Rows & Columns) |
| Relationships | One-to-Many | Many-to-Many | Many-to-Many |
| Data Access | Navigational | Navigational | SQL Queries |
| Flexibility | Low | Medium | High |
| Redundancy | High | Low | Low |
| Ease of Use | Hard | Complex | Easy |
8. Conclusion
The Network Model improved upon the Hierarchical Model by allowing many-to-many relationships and faster data retrieval. However, due to its complexity, it has been mostly replaced by the Relational Model (RDBMS), which is easier to manage and query using SQL.
Summary of the Network Model
✅ Best for complex relationships like Banking, Telecom, and Airlines
✅ Supports Many-to-Many relationships
❌ Hard to modify and complex query processing
❌ Not as flexible as Relational Databases