Hierarchical database architecture

This model of storing Enterprise data was invented by IBM in the early 60s and was used in their applications. The basic concept of hierarchical databases is that the data is organized in the form of a rooted tree. The root node is the beginning of the tree and then all the children are linked only to one of its parent nodes. This is a very unique way of storing and retrieving things.

If you have some background in computer science, trees are one of the unique ways of storing data so that it has some relation with each other (like a parent and child relationship).

This picture illustrates how data is organized in a typical HDBMS:

As we can see, the root node is the organization itself and all the data associated with the organization follows a tree structure which depicts several relationships. These relationships can be understood like this:

• Employee owns Laptop, Mobile phone, Workstation, and iMac
• Employee belongs to organization
• Many vendors supply different requirements:
  • Computer vendors supply iMac and Workstation
• Catering is in both India and USA; two vendors, The Best Caterers and Bay Area Caterers, serve these

Even though we have expressed multiple types of relationships in this one gigantic data store, we can see that the data gets duplicated and also querying data for different types of needs becomes a challenge.

Let's take a simple question like: Which vendor supplied the iMac owned by Employee-391?

In order to do this, we need to traverse the tree and find information from two different sub-trees.