Software Engineering

1.INTRODUCTION 1.a) DATA FLOW DIAGRAM
Data flow diagrams illustrate how data is processed by a system in terms of inputs and outputs.Data flow diagram are used widely for modeling the requirements.the DFD is also known as a data flow graph or a bubble chart.
Data Flow Diagram Notation
We can use two different types of notations on our data flow diagrams: Yourdon & Coad or Gane & Sarson.
Process Notations
1) Process
A process transforms incoming data flow into outgoing data flow.

Yourdon and Coad Process Notations

Gane and Sarson Process Notation

2)Datastore Notations
DataStore
Datastores are repositories of data in the system. They are sometimes also referred to as files.

Yourdon and Coad Datastore Notations

Gane and Sarson Datastore Notations

3)Dataflow Notations
Dataflow
Dataflows are pipelines through which packets of information flow. Label the arrows with the name of the data that moves through it.

4)External Entity Notations
External Entity
External entities are objects outside the system, with which the system communicates. External entities are sources and destinations of the system's inputs and outputs.

1.b) ENTITY RELATIONSHIP DIAGRAM
Entity–relationship model (ER model) in software engineering is an abstract way to describe a database. This article refers to the techniques proposed in Peter Chen's 1976 paper.An ER model is an abstract way to describe a database.
There are three basic elements in ER models:

 Entities are the "things" about which we seek information.
 Attributes are the data we collect about the entities.
 Relationships provide the structure needed to draw information from multiple entities.

Symbols Used In ERD:

1.c) OBJECT ORIENTED DESIGN
Object-oriented design is the process of planning a system of interacting objects for the purpose of