DDC 2453 – System Analysis and Design

Main ReferenceDennis, Wixom, Roth, System Analysis and Design, Third Edition, Wiley

PlanningPlanningChapter 1

The Systems Development Life Cycle

(SDLC)The SDLC is composed of 4

fundamental phases:

Phase 1: PlanningPhase 2: AnalysisPhase 3: DesignPhase 4: Implementation

The planning phase:

•understanding why an information system should be built.

•determine how project team builds the information system.

•2 planning steps:project initiationproject management

Phase 1: Planning

2 Planning stepsDuring project initiation:

• identify system’s business value to the organization (COST: lower/increase revenue?)

During project management:

Project manager

Phase 1: Planning

creates work planstaffs the project

put techniques to help project team control & direct the project through the entire SDLC

Answers the questions of:

Phase 2: Analysis

investigates current system

identifies improvement opportunities

develops a concept for new system

The project team

who use the system

what the system do

where & when it will be used

The system proposal is the initial deliverable – describes business requirements the new system should meet

3 Analysis Steps:1. Analysis Strategy: analyse the

current system2. Requirements gathering:

develop concept for new system based on the analysis of the information

3. System proposal: project sponsor & other key individuals decide whether to continue the project or not

Phase 2: Analysis

4 Design Steps

Phase 3: Design

4. Program Design: define what programs need to be written and what they will do

1. Design Strategy: identify whether system will be developed inside or outside company

2. Architecture Design: describe the hardware, software, and network infrastructure to be used3. Database & File

Specification: define what & where data will be stored

In this phase:

•the system is developed or purchased (in case of packaged software)

•usually the longest and most expensive part of the process

•has 3 steps:

Phase 4: Implementation

System constructionInstallation

Support Plan

3 Implementation Steps:1. System Construction:

System is built and tested to make sure it performs as designed

2. Installation: Prepare to support the installed system

3. Support Plan: Includes a post-implementation review

Phase 4: Implementation

(e.g. modem, if it needs to go online)

A methodology is a formalized approach to implementing the SDLC1. Systems Development 2. Data-centered3. Object-oriented

Methodologies

System Development Methodology:

•Waterfall development

•parallel development

•phased development

•prototyping-based

•throwaway prototyping

•agile development

Methodologies

Waterfall development:• the analysts and users proceed from one

phase to the next.

• Advantages:1. System requirements are identified long before programming begins.2. Minimized changes on requirements as the project proceeds.

• Disadvantages:1. Design must be completely specified before programming begins.2. Take longer time between the completion of the system proposal in the analysis phase and the delivery of the system.

Structured Methodologies

Waterfall development:

Structured Methodologies

Parallel development:• Longer time elapses between the

analysis phase and the delivery of the system

Structured Methodologies

Phased development: •adjust the SDLC phases to get some part of system developed quickly and into the hands of the users.

•analysts use special techniques and computer tools to speed up the analysis, design, and implementation phases, such as CASE (computer-aided software engineering) tools.

•Problem: managing user expectations.

RAD Methodologies

Phased development: •breaks overall system into a series of versions developed sequentially.

•the team categorizes the requirements into a series of versions.

•when each version is completed, the team begins on a new version.

RAD Methodologies

Phased development:

RAD Methodologies

Prototyping-based: •perform the analysis, design and implementation phases concurrently.

•all 3 phases are performed repeatedly in a cycle until the system is completed.

•a prototype is a smaller version of the system with a minimal amount of features.

•Advantage: provides system for users to interact with, even if it is not ready for use.

•Disadvantage: many initial design decisions prove to be poor ones.

RAD Methodologies

Prototyping-based:

RAD Methodologies

Throwaway Prototyping: •similar to prototyping based methodologies.

•main difference: Information System is completed during a different point in the SDLC.

•has thorough analysis phase.

RAD Methodologies

•streamline the SDLC by eliminating the modeling and documentation overhead and the time spent on those tasks.

•projects emphasize simple, iterative application development.

•uses extreme programming (XP).

Agile Methodologies

was founded on 4 core values:

communicationsimplicityfeedbackcourage

Extreme Programming (XP): •Key principles:

Agile Methodologies

•continuous testing

•simple coding

•close interaction with the end users to build systems very quickly

Clarity of User Requirement•RAD and throwaway prototyping are usually more appropriate when user requirements are unclear as they provide prototypes for users to interact early in the SDLC.

Methodologies

System Complexity•Complex systems require detailed analysis & design.

System Reliability•Throwaway prototyping: most appropriate when system reliability is a high priority.

•Prototyping-based: generally not a good choice as they lack of careful analysis & design phases.

Short Time Schedules•RAD: well suited for projects with short time schedules as they increase speed.

•Waterfall-based: the worst choice when time is limited as they do not allow for easy schedule changes.

Schedule Visibility•RAD move many critical design decisions earlier in the project; this helps project managers recognize risk factors and keep expectations high

Methodologies

Project Team Roles

•The Systems Development Lifecycle consists of 4 stages: Planning, Analysis, Design, and Implementation

•There are 6 major development methodologies: the waterfall method, the parallel development method, the phased development method, prototyping-based, throwaway prototyping, and agile development.

•There are 5 major team roles: business analyst, systems analyst, infrastructure analyst, change management analyst and project manager.

Summary