Software Design Methodologies and Testing

Software Design
Methodologies and Testing
Prof. Prashant J. Gadakh
International Institute of Information Technology
http://www.isquareit.edu.in/

Introduction To Software Design
• Deriving a solution which satisfies software requirements.
• Software Design is a process of describing, organizing and
structuring the components of a system.
• Software Design are like set of blueprints in which various
components of the system are shown.

Stages of Design
• Problem understanding
• Look at the problem from different angles to discover the
design requirements.
• Identify one or more solutions
• Evaluate possible solutions and choose the most
appropriate depending on the designer's experience and
available resources.

Stages of Design (Cont..)
• Describe solution abstractions
• Use graphical, formal or other descriptive notations to
describe the components of the design.
• Repeat process for each identified abstraction
Until the design is expressed in primitive terms.

The Design Process
• Any design may be modeled as a directed graph made up of
entities with attributes which participate in relationships.
• The system should be described at several different levels of
abstraction.
• Design takes place in overlapping stages. It is artificial to
separate it into distinct phases but some separation is
usually necessary.

Phases in the Design Process
Architectural
design
Abstract
specificatio
n
Interface
design
Component
design
Data
structure
design
Algorithm
design
Sy stem
architecture
Software
specification
Interface
specification
Component
specification
Data
structure
specification
Algorithm
specification
Requirements
specification
Design activities
Design products

PROCEDURAL DESIGN
METHODOLOGY
• A design methodology combines a systematic set of
rules for creating a program design with diagramming
tools needed to represent it.
• Procedural design is best used to model programs that
have an obvious flow of data from input to output.
• It represents the architecture of a program as a set of
interacting processes that pass data from one to another

Design Tools
• The two major diagramming tools used in procedural design
are as follows.
1. Data Flow Diagrams
2. Structure Charts (Flow Chart).

Data Flow Diagrams
• A data flow diagram (or DFD) is a tool to help you
discover and document the program’s major processes.
The following table shows the symbols used and what each
represents.

Sr.
NO
Symbol Used Meaning Example
1
An entity. A source of data or
a destination for data.
2
A process or task that is
performed by the system.
3 A data store, a place where data is
held between processes.
4
A data flow.

Relationship and Rules
• The DFD may be used for any level of data abstraction. DFD can
be partitioned into levels. Each level has more information flow
and data functional details than the previous level.
Highest level is Context Diagram. Some important points are:
• 1 bubble (process) represents the entire system.
• Data arrows show input and output.
• Data Stores NOT shown. They are within the system.

Software Design Methodologies and Testing

Level 0 DFD
• Next Level is Level 0 DFD. Some important points are:
• Level 0 DFD must balance with the context diagram it
describes.
• Input going into a process are different from outputs leaving
the process.
• Data stores are first shown at this level.

Level 1 DFD
• Next level is Level 1 DFD. Some important points are:
• Level 1 DFD must balance with the Level 0 it describes.
• Input going into a process are different from outputs leaving
the process.
• Continue to show data stores.

Difference Between DFD & Flow
Chart
• A DFD may look similar to a flow chart. However, there is a significant difference
with the data flow diagram. The arrows in DFDs show that there is a flow of data
between the two components and not that the component is sending the data
that must be executed in the following component.
• A component in DFD may not continue execution when sending data and during
execution of the component receiving the data. The component sending data can
send multiple sets of data along several connections. In fact, a DFD node can be
a component that never ends. In DFDs, all arrows must be labelled.

Structure Chart
• Structural Chart is principle tool of structure design.
• Elements are ,
1. Module
2. Data
3. Flag

• 1. Flag going from caller to
• called
• 2. Data going from caller to
called
• 3. Data going from called to
caller

Design methods: Object-Oriented
Design

Unified Modeling Language
Introduction
What is UML?

 Is a complete Language for capturing knowledge (semantics)
about a subject and expressing knowledge (syntax) regarding
the subject for the purpose of communication
 Applies to Modeling – process of understanding a subject (or
a system)
 Is Unified – remaining the same at each stage of development

Background
• 1965 - The first object-oriented programming language,
Simula I, was introduced
 Object-oriented Analysis & Design (OOAD) by Grady Booch.
 The Object Modeling Technique (OMT) by James Rumbaugh.
 The Object-oriented Software Engineering method (OOSE) by
Ivar Jacobson

OO Analysis vs. OO Design
 Analysis refers to
understanding
the problem.
 Design refers to
coming up with
the solution.
REQUIREMENTS
and
ANALYSIS
DESIGN
IMPLEMENTATION
TESTING

OO Analysis vs. OO Design
 Jacobson (OOSE) good at high-level design
 Rumbaugh (OMT) good at the middle ground
 Booch (OOAD) good at low-level design

1994 : Booch + Rumbaugh = Unified Method 0.8
1995 : + Jacobson = UML 0.8
Receiving a feedback from IBM, Microsoft, Oracle, HP
and other companies
1996 : UML 0.9
1997 : UML 1.0
Object Management Group (OMG) joined UML project
1997 : UML 1.1
UML is running under the OMG Revision Task Force
Improving semantics and flexibility
2003 : UML 2.0

Relationship Among UML Diagrams
• Structural Diagram
• Behaviour Diagrams

Static and Dynamic Modelling
• Static Modelling:-
Static Modelling is used to represent the static constituents
of a Software such as :
1.Classes, 2.Objects, 3.Interfaces and 4.Their relationship
with each other.

Static and Dynamic Modelling
• Dynamic Modelling:-
Dynamic Modelling is used to represent the behaviour of the static
constituents of a software ,
Dynamic Modelling Represent Following Diagrams,
1. Interaction Diagram:- Sequence and Collaboration Diagram.
2. Use Case Modelling
3. Activity Diagram

About I²IT
I²IT aspires to be an academic leader recognized for innovation, quality teaching
and research, holding high moral values and a forward thinking institution that
explores creative approaches for the future.
• Address: P-14, Rajiv Gandhi Infotech Park, Phase – 1, Hinjawadi, Pune – 411057,
India
• Phone: +91 20 2293 3441 / 2 / 3
• Email: info@isquareit.edu.in
• Web: www.isquareit.edu.in

Software Design Methodologies and Testing

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