What is bottom-up construction ?
Bottom-up design is an approach in which a system or process is built from smaller, simpler units or components. This approach starts with the most basic elements and assembles them step by step into more complex structures.

This process contrasts with the top-down approach, in which a system or process starts from a higher level or structure and is broken down into its individual components.
Bottom-up constructs are used in various disciplines and application areas, for example in programming, in project management or in psychology in the perception and processing of information. In programming, for example, this means starting with simple functions and algorithms and combining them to create more complex systems.

