csis 3600 systems analysis and design the systems development life cycle intellectual property of...

CSIS 3600 Systems CSIS 3600 Systems Analysis and DesignAnalysis and Design

The Systems Development Life Cycle

Intellectual Property of Dr. Meg Murray, dated August 2002

Methodologies, Techniques & Methodologies, Techniques & ToolsTools

The Systems Development structure includes:

Methodology

Techniques

Tools

Methodologies, Techniques & Methodologies, Techniques & ToolsTools

• Methodologies are comprehensive, multi-step approaches that guide the systems development process. Most incorporate many techniques.

• Techniques are the particular processes that are used to complete the work of systems development. Techniques describe the activities and tasks that will be employed and define deliverables.

• Tools are what you have that help you accomplish your tasks. Many software tools are now available that facilitate the development of deliverables. CASE tools fall under this category.

What Is a Methodology?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.

• A Product Development Methodology is available for review on the class web site.

Methodologies• Most software development consultant agencies

use a methodology template. An example is http://www.prestwood.com/products/psdm/

• A good collection of resources related to methodologies can be found at http://www.methodology.org

• Microsoft serves as a framework for many organizations: http://www.microsoft.com/business/microsoft/mcs/msf.asp

http://www.prestwood.com/products/psdm/





http://www.methodology.org/

http://www.microsoft.com/business/microsoft/mcs/msf.asp

http://www.microsoft.com/business/microsoft/mcs/msf.asp

What are TechniquesWhat are Techniques

Techniques are the processes used to carry out the methodology. They include:

– Project Selection Process– Project Plan– System Requirements Definition– System Models

What are ToolsWhat are Tools

Tools help in the system development process. These tools include CASE tools, diagramming tools, etc.

A listing of Case Tools is available at:

http://www.cs.queensu.ca/Software-Engineering/toolcat.html



Structured Design

• Projects move methodically from one to the next step

• Generally, a step is finished before the next one begins

PowerPoint Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design

Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Waterfall Development Method



Pros Cons

Design must be specified on paper before programming begins

Pros and Cons of the Waterfall Method

Identifies systems requirements long before programming begins

Long time between system proposal and delivery of new system



Systems Development Life CycleSystems Development Life Cycle

• The SDLC came out in the late 1960s and early 1970s and was really the first documented structured approach.

• It is very logical and comprehensive.

• It grew up in the era of large mainframes but

as a framework, it is applicable to today’s

distributed systems.

Major Attributes of the LifecycleMajor 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



•Six Stage Plan (more general version):I. Preliminary Investigation

• gain understanding of problem domain and current organizational environment.

II. Systems Analysis• define business requirements, evaluate alternatives,

prepare functional requirementsIII. System Design

• define technical specificationsIV. System Construction

• build or select software, test system and train usersV. System Implementation

• get the system running and begin to use the systemVI. Evaluation

• evaluate how the system is meeting objectives and make adjustments



I. Project Identification and Selection

II. Project Initiation and Planning

III. Analysis

IV. Logical Design

V. Physical Design

VI. Implementation

VII. Maintenance (and evaluation)

• Four Stage Plan (the short version):– I. Systems Planning

– II. Analysis– III. Systems Design– IV. Systems Implementation




Project PhasesProject Phases• Planning

– Why build the system?• Analysis

– Who, what, when, where will the system be?• Design

– How will the system work?• Implementation

– System delivery



• Identifying business value

• Analyze feasibility

• Develop work plan

• Staff the project

• Control and direct project

PlanningPlanning



Deliverables PDeliverables Planning – lanning – Business ValueBusiness Value

• Identification and prioritization of information system needs

• Problem is identified and articulated

• Business case or system justification

Deliverables PDeliverables Planninglanning

• Project scope

• Project feasibility

• Selection of system development participants

• Project (work) plan

• Analysis

• Information gathering

• Process modeling

• Data modeling

AnalysisAnalysis



Deliverables - AnalysisDeliverables - Analysis

• Description of the current system/environment

• Determine and structure functional requirements

• Identification of alternatives• Initial system models are built

– Use case models – Other models (UML – class diagrams,

sequence diagrams, etc…

• Physical design

• Architectural design

• Interface design

• Database and file design

• Program design

DesignDesign



Deliverables - DesignDeliverables - Design

• Technical detailed specifications of all systems elements (programs, files, network, system software, etc.)

• Interface Design

• Database and file design

• Construction

• Installation

• Maintenance and Evaluation (not outlined in text)

ImplementationImplementation



DelivDeliverables - Implementationerables - Implementation

• Software code• Documentation• Installation plan• Testing plan• Training procedures• Initial support capabilities outlined• Maintenance Plan• Evaluation Plan

Processes and DeliverablesProcesses and Deliverables

Process Product

Planning

Analysis

Design

Implementation

Project Plan

System Proposal

System Specification

New System and Maintenance

Plan



Note on MaintenanceNote on Maintenance

Maintenance:– system is systematically repaired and

improved.

– This is the evolution of the information system and all previous phases are repeated

Concluding Notes on the SDLC

The SDLC provides a framework. Systems development is cyclical. Phases overlap and flexibility must be built into the design process. The SDLC provides a convenient checklist of tasks to be undertaken or ignored as appropriate.

Concluding Notes on the SDLCThe SDLC is most appropriate in situations where the information systems requirements are predicable (in Transaction Processing and MIS type systems).

It can be adapted to meet other needs and parts of the SDLC are included in most all system development methodologies.

Concluding Notes on the SDLC

One criticism of SDLC is that it tends to focus too little on good analysis and design resulting in a system that does not match users’ needs and requires extensive maintenance (software repair, patches, etc.).

Some estimates suggest that maintenance costs account for as much as 70% of system development costs.

Alternatives to the SDLCAlternatives to the SDLC• RAD and JAD – Strategies for reducing the

time it takes to deliver systems. Focused on extensive user involvement, prototyping and integrating CASE tools.

• Prototyping – iterative process of system development in which a draft working system is developed and modified

• Object Oriented Design and Analysis – very similar and incorporates the phases of the SDLC

• Agile Methods

Alternatives to the SDLCAlternatives to the SDLC

• Rapid Application Development (RAD)

• Phased Development

• Prototyping

• Throw-Away Prototyping



Rapid Application DevelopmentRapid Application Development

• Critical elements– CASE tools– JAD sessions– Fourth generation/visualization

programming languages– Code generators



How Prototyping WorksHow Prototyping Works



Throwaway PrototypingThrowaway Prototyping



Object-Oriented Analysis Object-Oriented Analysis and Designand Design

• Attempts to balance emphasis on data and process

• Uses Unified Modeling Language (UML) for diagramming – Use-case Driven– Architecture Centric– Iterative and Incremental

• Focus of this course



Concluding Notes

Not all system requirements can be stated up front, and problems often appear towards the end of the process.

Flexibility, common sense and a focus on the goal at hand are the real tricks to making your systems development methodology work.

Quotes of the WeekQuotes of the Week

"When a new system concept or new technology is used, one has to build a system to throw away, for even the best planning is not so omniscient as to get it right the first time. The management question, therefore, is not whether to build a pilot system and throw it away. You will do that. The only question is whether to plan in advance to build a throwaway, or to promise to deliver the throwaway to customers." Brooks cited in Pressman (Software Engineering : A Practitioner’s Approach, 4th Edition, 1997).--------"When faced with a problem you do not understand, do any part of it you do understand, then look at it again." Robert Heinlen

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