3.3.4 E-R Model (ERM)
An entity-relationship diagram is an excellent tool for planning and designing a database, particularly when used in conjunction with data normalization.
The entity-relationship model starts with the entities, data normalization starts with the attributes, and the two tools tend to verify each other. The entities, attributes, and relationships of the entity-relationship model map smoothly to a physical database.
During the systems analysis phase, an entity-relationship diagram gives the analyst a clear, high-level view of the data. Used in conjunction with data flow diagrams, an entity- relationship model gives the analyst an alternative logical view of the system. If a great deal is known about the data but not much about the processes, an entity-relationship diagram is an excellent starting point for modelling the system.

3.3.4.1 Database Design
Database design is the process of gathering data requirements for an organization, a business process, or a proposed information system, and transforming these requirements into a set of speciï¬cations that can be used to create a database. The goal of database design is not only to provide the ability to capture all necessary information, but to organize that information in an efï¬cient and usable way. To do so would require knowledge about what the information and how it will be used, as well as information about the computing environment in which the database will be implemented (TISCH Williams 1999).
3.3.4.2 Database Design Methodologies
This is an overview of the various ways in which database can be designed which include:
=> Logical Database Design
=> Physical Database Design Logical database design
Logical or conceptual database design is concerned with deï¬ning and documenting the database in user terms. The objective is to formally deï¬ne the user’s understanding of the data and how the various data elements and composites are interrelated (TISCH Williams 1999).