SDLC: System Development Life Cycle

Dr. BilalIS 582Spring 2006

Systems Analysis & Design

Method used to create and maintain systems that perform specific functions. Examples: processing orders, employee

payroll, acquisitions, cataloging, etc. Use of application software designed

to help employees to complete these functions

Application Software

Developed internally: in businesses & other organizations

Developed externally: by specific companies

Off-the-shelf application software may not fit the needs of all organizations

Components of IS Application

Six components: System software Application software Hardware

Components of IS Application Documentation & training manuals People who use the system Technical personnel

People who keep system operating; trouble shooters

Controls Prevent fraud and theft

Software Engineering Process

Components Methodologies Techniques Tools

Methodologies

Approaches taken by system developers to develop the information system Qualitative (e.g., interviewing users) Quantitative (e.g., collect data via direct

observations of users)

Techniques

Based on methodology chosen Processes or procedures followed to

gather data about current and/or potential users Design interviews, observations, focus

groups

IS Tools

Computer-aided software engineering (CASE) Automate software development Examples:

Excel Software http://www.excelsoftware.com/

System Concepts

Decomposition Modularity Coupling Cohesion

Decomposition

Process of breaking down a system into subsystems or smaller components

Smaller components may be broken down into small parts

Modularity

A result of decomposition Divides system into modules Makes system easier to understand,

design/redesign, build/rebuild

Coupling

The degree subsystems or modules are dependent on each other in terms of operation (physically separate)

Subsystems should be as independent as possible If one module fails, the other modules

remain in operation

Cohesion

“The extent to which a system or subsystem performs a single function.”

Examples: Check-in Check-out

Important Concepts

Data Information Database Data flow

Important Concepts

Processing logic Process-oriented approach to SD Data-oriented approach to SD

Systems Development Life Cycle(Valacich, George, & Hoffer, 2006)

Phase 1: Planning & Selection

Product identification and selection Product initiation and planning

Identify potential development projects Classify and rank projects Select projects for development

Phase 2: Systems Analysis

Determine system requirements Select appropriate methods to elicit

system requirements from users of system Interviews, focus groups, surveys,

discussions, or other techniques

Phase 3: Systems Design

Structure system requirements Modeling processes

Develop data flow diagrams (DFDs) based on specific rules and guidelines that lead to accurate and well-structured process models.

Use DFDs to support analysis of IS

Phase 3: Systems Design Use logic modeling and/or other

modeling techniques to represent data Process modeling Conceptual data modeling

Select best alternative design strategy using both qualitative and quantitative methods

Phase 3: Systems Design

Design the human interface Design the interaction (dialogue) Build a prototype Perform usability testing Design the database

Phase 4: System Implementation & Operation

Implement system: Design specifications are turned into

working computer code Test code for errors and other

problems Use a sample data set

Phase 4: System Implementation & Operation

Install system Prepare documentation Train users of the system Provide support Maintain system on a regular basis

Class Activity

Work in a group Examine the SDLC Map each phase to the design and

development or acquisition of a new automated system for a specific agency or library