DR. SANGEETA ARORA �(HOD, P.G DEPT OF COMPUTER SCIENCE & IT)�

System Analysis and Design

KEY IDEAS

• Many failed systems were abandoned because analysts tried to build wonderful systems without understanding the organization.
• The primarily goal is to create value for the organization.

KEY IDEAS

• The systems analyst is a key person analyzing the business, identifying opportunities for improvement, and designing information systems to implement these ideas.
• It is important to understand and develop through practice the skills needed to successfully design and implement new information systems.

THE SYSTEMS DEVELOPMENT LIFE CYCLE

MAJOR ATTRIBUTES OF THE LIFECYCLE

• The project
• Moves systematically through phases where each phase has a standard set of outputs
• Produces project deliverables
• Uses deliverables in implementation
• Results in actual information system
• Uses gradual refinement

PROJECT PHASES

• Planning
• Why build the system?
• Analysis
• Who, what, when, where will the system be?
• Design
• How will the system work?
• Implementation
• System delivery

PLANNING

• Identifying business value
• Analyze feasibility
• Develop work plan
• Staff the project
• Control and direct project

ANALYSIS

• Analysis
• Information gathering
• Process modeling
• Data modeling

DESIGN

• Physical design
• Architectural design
• Interface design
• Database and file design
• Program design

IMPLEMENTATION

• Construction
• Installation

PROCESSES AND DELIVERABLES

THE EVOLUTION OF SYSTEM DEVELOPMENT

WHAT IS A METHODOLOGY?

• A formalized approach or series of steps
• Writing code without a well-thought-out system request may work for small programs, but rarely works for large ones.

STRUCTURED DESIGN

• Projects move methodically from one to the next step
• Generally, a step is finished before the next one begins

WATERFALL DEVELOPMENT METHOD

PROS AND CONS OF THE WATERFALL METHOD

Pros

Cons

Identifies systems

requirements long

before programming

begins

Design must be

specified on paper

before programming

begins

​

Long time between

system proposal and

delivery of new

system

ALTERNATIVES TO THE SDLC

• Rapid Application Development (RAD)
• Phased Development
• Prototyping
• Throw-Away Prototyping

RAPID APPLICATION DEVELOPMENT

• Critical elements
• CASE tools
• JAD sessions
• Fourth generation/visualization programming languages
• Code generators

RAPID APPLICATION DEVELOPMENT CATEGORIES

• Phased development
• A series of versions
• Prototyping
• System prototyping
• Throw-away prototyping
• Design prototyping

HOW PROTOTYPING WORKS

THROWAWAY PROTOTYPING

OBJECT-ORIENTED ANALYSIS AND DESIGN

• Attempts to balance emphasis on data and process
• Uses Unified Modeling Language (UML) for diagramming
• Use-case Driven
• Architecture Centric
• Iterative and Incremental

BASIC CHARACTERISTICS OF OBJECT-ORIENTED SYSTEMS

KEY ELEMENTS

• Classes -- template to define objects
• Instances -- specific examples of class members
• Objects -- building block of the system
• Attributes -- describe data aspects of the object
• Methods -- the processes the object can perform
• Messages -- instructions sent to or received from other objects

A CLASS AND ITS OBJECTS

PATIENT 1: TOP PACKAGE: PATIENT

​

-Name = Teresa Marks

-Birthdate = March 16, 1975

-Phone number = 314-997-3456

PATIENT 2: TOP PACKAGE: PATIENT

​

-Name = Mel Bourne

-Birthdate = May 11, 1965

-Phone number = 314-997-3219

​

​

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Attributes

Methods

Class

Instantiated Objects of the Class

THE KEY TO REUSABILITY

• Information hiding is the principle that only information required to use the object is available outside the object
• Encapsulation is the mechanism that combines data and processes in a single object

CLASS HIERARCHY

INHERITANCE

POLYMORPHISM

THANK YOU