Bottom up is an analytical approach where parts of the system are defined in details. Once these parts are designed and developed, then these parts or components are linked together to prepare a bigger component. This approach is repeated until the complete system is built. A bottom up model is based on a composition approach.
Hybrid is an analytical approach that combines the top down and the bottom up approach. Some parts are based on composition approach while other parts are based on decomposition approach.
Top down is an analytical approach where design starts from the system as a whole. The system is then divided into smaller sub-applications with more details. Each part again goes through the top down approach till the complete system is designed with all minute details. Top down approach is also termed as breaking the bigger problem into smaller problems and solving them individually in a recursive manner. A top down model is based on a decomposition approach.
Ontology