Suppose you were assigned to develop a logical model of the registration system at a school or college. Would you be better off using a top-down approach, or would a bottom-up strategy be better? What would influence your decision?
A logical model of a system needs to show what a system needs to do in order to meet the needs of its users. A top-down approach looks at the entire system and drills down to the different processes that make up the system. Using a Data Flow Diagram (DFD), a system analyst uses graphical tools and symbols “to show how the system transforms input data into useful information” (Tilley, 2017)
According to Comparing Top-down with Bottom-up Approaches: Teaching Data Modeling, “In contrast, bottom-up approaches view database design as proceeding from an initial analysis of lower-level conceptual units, such as attributes and functional dependencies and then moving towards an acceptable logical data model through logical groupings of associated attributes.” (Kung et al., 2013). Though a bottom-up approach can help reduce redundancies in system processes as they are grouped together, a top-down approach allows for designing systems that are complex by exploding processes done to their functional primitives.
To make a logical model of a school registration system, getting an overview of what the system is supposed to do, then leveling down each of the processes in a detailed data flow diagram makes leveling of the increasingly complex processes of the system easier to understand, document and transition into a physical model.
Sources
Kung, H.-J., Kung, L., & Gardiner, A. (2013). Comparing Top-down with Bottom-up Approaches: Teaching Data Modeling. 11.
Tilley, S. (2017). Systems Analysis and Design (12th ed.). Cengage.
