What are the key characteristics of hierarchical database models?

Hierarchical database models are characterised by their tree-like structure, parent-child relationships, and single parent rule.

Hierarchical database models are a type of database model that organises data in a tree-like structure. This structure is based on the concept of parent-child relationships, where each child can have only one parent, but each parent can have multiple children. This is also known as the single parent rule. The topmost node in this structure is known as the root, and it has no parent. All other nodes in the structure are connected to the root through a series of parent-child relationships.

One of the key characteristics of hierarchical database models is their simplicity. The tree-like structure is easy to understand and navigate, making it a popular choice for databases that require a high level of organisation. This structure also makes it easy to add, delete, and modify data, as changes can be made to a single node without affecting the rest of the database.

Another key characteristic of hierarchical database models is their efficiency. Because each node has a single parent, data retrieval is fast and straightforward. This makes hierarchical databases particularly useful for applications that require quick and efficient data retrieval, such as online banking systems or airline reservation systems.

However, hierarchical database models also have some limitations. The single parent rule means that they are not suitable for databases that require many-to-many relationships. Additionally, because each node is connected to its parent, changes to the database structure can be complex and time-consuming. For example, if a node needs to be moved to a different part of the tree, all of its child nodes must also be moved.

In summary, hierarchical database models are characterised by their tree-like structure, parent-child relationships, and single parent rule. They are simple and efficient, but their structure can also make them inflexible and complex to modify.