SDLC: System Development Life Cycle Dr. Bilal IS 582 Spring 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

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