Online Examination System 9. Project Life Cycle ( DFD & ERD) 9.1 ER Modeling In software engineering, an entity – relationship model (ER model) is a data model for describing the data or information aspects of a business domain or its process requirements, in an abstract way that lends itself to ultimately being implemented in a database such as a relational database. The main components of ER models are entities (things) and the relationships that can exist among them. An Entity-relationship model (ERM) is an abstract and conceptual representation of data. ER modeling is a DB modeling method, used to produce a type of conceptual schema of a system. Diagrams created by this process are called ER diagrams Sequence: Conceptual data model (i.e. ER) is, at a later stage (called logical design), mapped to a logical data model, (e.g. relational model); this is mapped to a physical model in physical design. ER Model is used to interpret, specify & document requirements for DBs irrespective of DBMS being used. The ER diagram of the project “Online Examination System” is shown in Fig 9.1.