new phase ii-2010

Mini Project-1

Phase – IIDesign Phase

Dept. Of Computer Science and Engineering

Objective

• Design allows an engineer to model the system or product that is to be built

• To produce a solution to a problem given in SRS document.

• To tell “how” a software system works.

Case Study: Guess the site!

• What is the single most important reason for this disaster?

•Design Flaw?!!!!

Why Design Is Important ?

• Design is the place where product (software) quality is established.

• A good design is

• understandable

• easy to implement

• reliable and

• allows smooth evolution

Good design is key to successful product

Poor design results to unstable system:

• Unstable System will fail when small changes are made.

• Unstable System will be difficult to maintain.

• Unstable System’s quality cannot be assessed until late in the software process.

What is it ?

• Design of the system is essentially a blueprint or a plan for a solution for the system.

• Design tells how the system is implemented.

• The design model provides details about software data structures ,architectures, interfaces and components that are necessary to implement the system.

Conceptual to Technical design

How to Design ?• A design process for software systems has

two levels

• Top – level design ( System design)

• Detailed design ( Logic design)

Top – level design

• System is a set of modules with clearly defined behavior which interact with each other in a defined manner to produce some behavior or services for its environment

• Decide which modules are needed for the system, the specifications of these modules, and how the modules should be interconnected.

Detailed Design

• In this level, the internal design of the modules, or how the specifications of the modules can be satisfied, is decided.

• It specify the processing logic and data structures so that the design is sufficiently complete for coding

Output of the Design Phase

• SDD (software Design Document) contain

• Different modules and Interfaces with each other.

• Data structures.

• Different classes and relationship between each other.

Deliverables : (Design documents)Top level design Detailed design

•Architecture

•Block Diagram •ER diagram

•Structure charts •Flowcharts/

Algoriths

•Data flow

diagram

Students need to do the

things which indicated in

green

•Class diagrams

Case study : Data flow modeling

• A restaurant owner feels that some amount of automation will help make his business more efficient .

Data flow diagram

Data flow Diagram

• For any known problem

Object oriented Modeling

• System is viewed as a set of objects• Objects interact with each other through the

services they provide• Object oriented systems are easier to build

& maintain• Object oriented design and implementation

is easy as objects are more stable than functions

Contd..

• UML (Unified modeling Language is used for OOM)

• -Class diagrams

• -Activity diagrams

• -Sequence diagrams

• -Deployment diagrams• Class diagrams are used to represent the

structure of the system

Class diagrams• Object (ask definition )• Class( ask definition ) • Services/ methods • Class diagram represent a structure of

the problem graphically using precise notation

Class name

attribute

operations

customer

Name:

Address:

Check_balance()

Credit_amt()

Relationship between different classes

• Generalization-specialization

• Aggregation

• Association

Generalization-specializationsymbol is used for representation. This shows inheritance property

example

Aggregation symbol is used for representation. This represents whole-part

relationship. If object is composed of many objects then aggregation is used

example

Associationshows static relation ship between different objects. Can be represented in different ways

cardinality

OO AnalysisFollowing steps are performed

• Identifying objects & classes

• Identifying structures

• Identifying attributes

• Identifying associations

• Defining services

Identifying Objects and classes

• Nouns represent entities in the problem space which will be modeled as objects

• Structures, devices, events, locations, organizational units are modeled as objects

• If the system does not need to keep information about some real-world entity or does not need any services from the entity, it should not considered as an object

Identify the structures

• Identify the hierarchies that exist between object classes

• Use generalization-specialization to represent inheritance

• Aggregation for whole – part relation ship

• Establish a relationship between objects using association

OO design

Problem description

Rough classes Class Diagrams

Noun identification technique

Specify associations

Example of drug storeask the students to identify the class, attributes,services

and relationships

How student should do ? Split each project batch into two sub batches in the first

week. Each sub batch has to do design independently. For

every SRS there will be two pre final designs accordingly.

The design done by one sub batch will be reviewed by the other sub batch and evaluator in the second week.

The group arrives at the final acceptable design combining the best from both the pre final designs.

The final design will be evaluated in the third week.

SRS Document

Pre final Design 2

Pre final Design 1

Final Design

Team Sub Batch 2

Divide Team into 2 Sub Batch es

Deliverables

• DFD

• Class diagram

• Algorithem/flowchart

• Data structures

• Files description(data file if exists)

schedule

Sl no Task Dates

1 Presentation on design phase and splitting of batches and assigning a design task

Week - 27th sept to 2nd oct

2 Pre-final design discussion with guide and team members

Week - 4th to 9th oct

3 Final design evaluation Week – 11th to 16th oct

Thank you