Online Examination System
Online Examination System
9. Project Life Cycle (DFD & ERD)
9.1 ER Modeling Insoftware engineering, anentityrelationship
model(ER model) is adata modelfor 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 adatabasesuch as arelational database. The
main components of ER models areentities(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 diagramsSequence: 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.
Fig 9.1:- ER diagram for online examination system.
9.2 Data Flow Diagram (DFD)
Adata flow diagram(DFD) is a graphical representation of the
"flow" of data through aninformation system, modeling
itsprocessaspects. Often they are a preliminary step used to create
an overview of the system which can later be elaborated.DFDs can
also be used for thevisualizationofdata processing(structured
design).A DFD shows what kind of information will be input to and
output from the system, where the data will come from and go to,
and where the data will be stored. It does not show information
about the timing of processes, or information about whether
processes will operate in sequence or in parallel.
Fig 9.2:- Data Flow Diagram for online examination system.
Fig 9.3:- Context diagram for online examination system.
Fig 9.4:- Level 1 DFD for online examination system.
Fig 9.5:- Level 2 DFD for process 2 (update subjects).
Fig 9.6:- Level 2 DFD for process 3 (update questions).
Fig 9.7:- Level 2 DFD for process 8 (exam process).
