Hierarchical & Network Model

Before the relational model became dominant, the hierarchical and network models were the primary ways to structure databases. The Hierarchical Model, as the name suggests, organizes data in a tree-like structure. Data is stored as records which are connected to one another through links. Each record type is a 'node' in the tree. A parent node can have multiple child nodes, but each child node can have only one parent. This one-to-many relationship structure is rigid but efficient for navigating down the tree. A classic example is an organization chart. This model is simple to understand but inflexible, as it cannot easily represent many-to-many relationships. The Network Model was developed to address this limitation. It is an extension of the hierarchical model, but it allows a child node (called a member) to have multiple parent nodes (called owners). This creates a more flexible graph-like structure, capable of modeling complex many-to-many relationships directly. While more flexible, the network model was also more complex to design and maintain. Navigating the database required programmers to write complex procedures that followed the data pointers or 'links' from record to record. Both models are considered legacy systems today, having been largely replaced by the more flexible and user-friendly relational model and modern NoSQL databases. However, understanding them provides valuable context for the evolution of database technology.