Topic9 SDLC

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STIM5013 IT For Manager

Discovering Computers 2010: Living in a Digital WorldChapter 14

1

Topic EightInformation Systems Development


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Obj ectives Overview

Describe the varioustools used in object

modeling

Explain the activitiesperformed in the

design phase

Recognize the developprograms activity is

part of systemdevelopment

Discuss the activitiesperformed in the

implementation phase

Discuss the purpose of the activities

performed in theoperation, support, and

security phase


3See Page 619for Detailed Objectives


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Wh at is System Development?

System development is a set of activitiesused to build an information system

A system is a set of components that

interact to achieve acommon goal

An informationsystem (IS) is a

collection of hardware, software,

data, people, andprocedures that worktogether to producequality information

System developmentactivities are grouped

into ph ases , and iscalled the systemdevelopment life

cycle (SDLC)


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5Pages 620 621Figure 12-1


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System development should follow three generalguidelines:


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Group activities or tasks into phases

Group activities or tasks into phases

Involve users

Involve users

Define standards

Define standards


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System development should involve representatives from eachdepartment in which the proposed system will be used


7Page 622Figure 12-2


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Pro ject management is the process of planning,scheduling, and then controlling the activities duringsystem development

To plan and schedule a project efficiently, the projectleader identifies:


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Project scope RequiredactivitiesTime estimatesfor each activity

Cost estimatesfor each activity

Order of activities

Activities thatcan take place atthe same time


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9Page 623Figure 12-3a

Click to view Web Link,click Chapter 12, Click WebLink from left navigation,then click Gantt Charts below Chapter 12

A popular toolused to planand schedule

the timerelationships

among projectactivities is a

Gantt chart


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10Page 624Figure 12-3b

Click to view Web Link,click Chapter 12, Click WebLink from left navigation,then click PERT Charts below Chapter 12

A PERT chartalso can be

used forplanning and

scheduling time


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Feasi b ility is a measure of how suitable thedevelopment of a system will be to theorganization


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Operationalfeasibility

Schedulefeasibility

Technicalfeasibility

Economicfeasibility


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Documentation is the collection andsummarization of data and information

A project notebook contains all documentation for asingle project

Users and IT professionals refer to existingdocumentation when working with and modifyingcurrent systems


12Page 625


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During system development, members of the projectteam gather data and information using severaltechniques



Reviewdocumentation Observe Survey

Interview JAD Sessions Research


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Wh o Initiates a SystemDevelopment Pro ject?

A user may request a new or modified system

Organizations may want to improve hardware, software, or other

technology

Situations beyond an organization s control might require a change

Management might mandate a change

A user may request a new or modified information system using a requestfor system services or a project request


14Page 626


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Wh o Initiates a SystemDevelopment Pro ject?




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Planning P h ase

The planning p h ase for a project begins when thesteering committee receives a project request

Four major activities are performed:


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Review and

approve theproject requests

Review and

approve theproject requests

Prioritize theproject requests

Prioritize theproject requests

AllocateresourcesAllocate

resources

Form a project

developmentteam

Form a project

developmentteam


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A nalysis P h ase

The analysis p h ase consists of two majoractivities:


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Conduct a preliminaryinvestigation

Determines anddefines the exactnature of the problemor improvementInterview the user whosubmitted the request

Determines anddefines the exactnature of the problemor improvementInterview the user whosubmitted the request

Perform detailedanalysis

Study how the currentsystem works

Determine the userswants, needs, andrequirementsRecommend a solution

Study how the currentsystem works

Determine the userswants, needs, andrequirementsRecommend a solution


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A nalysis P h ase



Click to view Web Link,click Chapter 12, Click WebLink from left navigation,then click Feasibility Study below Chapter 12


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A nalysis P h ase

Process modeling (structured analysis and design) is ananalysis and design technique that describes processesthat transform inputs into outputs


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Entity-relationship

diagrams

Data flowdiagrams

ProjectdictionaryClick to view Web Link,click Chapter 12, Click Web

Link from left navigation,then click Process Modelingbelow Chapter 12


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A nalysis P h ase

An entity-relations h ipdiagram (ERD) is a toolthat graphically shows

the connections amongentities in a systemEntities are objects inthe system that havedata




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A nalysis P h ase

A data flow diagram(DFD) is a tool thatgraphically shows the

flow of data in a system Data flows Processes Data stores Sources




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A nalysis P h ase

The pro ject dictionary contains all thedocumentation and deliverables of a project

Structured English is astyle of writing thatdescribes the steps ina process




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A nalysis P h ase

A decision ta b le is a table thatlists a variety of conditionsand the actions thatcorrespond to each condition

A decision tree also showsconditions and actions, but itshows them graphically


23Page 633


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A nalysis P h ase

Decision ta b le Decision tree


24Page 633Figures 12-10 12-11


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A nalysis P h ase

The data dictionary stores the data item s name,description, and other details about each dataitem




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A nalysis P h ase

A use case diagramgraphically shows howactors (users) interact

with the informationsystemDiagrams areconsidered easy tounderstand




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A nalysis P h ase

A class diagramgraphically showsclasses and subclasses

in a systemEach class can have oneor more subclassesSubclasses use

inheritance to inheritmethods and attributesof higher levels




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A nalysis P h ase

The system proposal assesses the feasibility of each alternative solution

The steering committee discusses the systemproposal and decides which alternative to pursue


29Pages 635 - 636

Packagedsoftware

Customsoftware Outsourcing

Click to view Web Link,click Chapter 12, Click WebLink from left navigation,then click Vertical Market Software below Chapter 12


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Design P h ase

The design p h ase consists of two major activities


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Acquire hardwareand software

Develop all of thedetails of the new

or modified

information system


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Design P h ase

To acquire the necessary hardware and software:


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Use researchtechniques such ase-zines

Identify technical

specifications

RFQ, RFP, or RFI issent to potentialvendors or VARs

Solicit vendorproposals Various techniquesare used todetermine the bestproposal

Test and evaluate

vendor proposals

Systems analystmakesrecommendation tosteering committee

Make a decision

Click to view Web Link,click Chapter 12, Click WebLink from left navigation,then click E-Zines below Chapter 12


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Design P h ase

The next step is to develop detailed designspecifications Sometimes called a physical design


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Databasedesign

Input and

outputdesign

Programdesign


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Design P h ase

Systems analysts typically develop two types of designs for each input and output


33Page 641Figures 12-18 12-19

Mockup Layout c h art


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Design P h ase

A prototype (proof of concept) is a working modelof the proposed system Prototypes have inadequate or missing documentation Users tend to embrace the prototype as a final system Should not eliminate or replace activities


34Pages 641 - 642


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Design P h ase

Computer-aided software engineering (CASE)tools are designed to support one or moreactivities of system developmentCASE tools sometimes contain the following tools:


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Projectrepository Graphics Prototyping

Qualityassurance

Codegenerator Housekeeping

Click to view Web Link,click Chapter 12, Click WebLink from left navigation,then click CASE Toolsbelow Chapter 12


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Design P h ase




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Design P h ase

Many people should review the detailed designspecifications

An inspection is a formal review of any systemdevelopment deliverable A team examines the deliverables to identify errors


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Implementation P h ase

The purpose of the implementation p h ase is toconstruct the new or modified system and thendeliver it


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Develop

programs

Develop

programs

Install andtest the new

system

Install andtest the new

systemTrain usersTrain users

Convert tothe newsystem

Convert tothe newsystem


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The program development life cycle follows thesesteps:


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1 Analyze the requirements

2 Design the solution

3 Validate the design

4 Implement the design

5 Test the solution

6 Document the solution


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Various tests should be performed on the newsystem


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Unit test

Verifies thateachindividual

program orobject worksby itself

Verifies thateachindividual

program orobject worksby itself

Systems test

Verifies thatall programsin an

applicationworktogetherproperly

Verifies thatall programsin an

applicationworktogetherproperly

Integrationtest

Verifies thatanapplication

works withotherapplications

Verifies thatanapplication

works withotherapplications

Acceptancetest

Checks thenew systemto ensure

that it workswith actualdata

Checks thenew systemto ensure

that it workswith actualdata


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Training involves showing users exactly how theywill use the new hardware and software in thesystem One-on-one sessions Classroom-style lectures Web-based training




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One or more of four conversion strategies can beused to change from the old system to the newsystem




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Operation, Support, and Security P h ase

The purpose of the operation, support, andsecurity p h ase is to provide ongoing assistance foran information system and its users after thesystem is implemented


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Performmaintenance

activities

Monitorsystem

performance

Assess systemsecurity

Click to view Web Link,click Chapter 12, Click WebLink from left navigation,then click Chief Security Officer below Chapter 12


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Operation, Support, and Security P h ase

A computer security plan should do the following:


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Identify allinformationassets of an

organization

Identify allsecurity risks

that may causean information

asset loss

For each risk,identify the

safeguards thatexist to detect,prevent, and

recover from aloss


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A lternatives to Conventional SDLCs

Four Possibilities:a. Prototypingb. Joint Application Design

c. Rapid ApplicationDevelopment

d. Component BasedDevelopment


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Prototyping

Working model of a proposed system

Instead of spending a lot of time producing very detailed

specifications, the developers find out only what the userswant developers quickly create a prototype.

This approach is also known as evolutionary development.


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Joint A pplication Design

Joint application design (JAD) is a group-based method forcollecting user requirements and creating system designs.

In contrast to the SDLC requirements analysis, JAD has agroup meeting in which all users meet simultaneously withanalysts.


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R apid A pplication Development

Rapid application development (RAD) is a methodology andtools that make it possible to develop systems faster,especially systems where the user interface is an importantcomponent.

Typical RAD packages include the following:

GUI development environment

Reusable componentsCode generatorProgramming language


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Component- based Development

Components are self-contained packages of functionalitythat have clearly defined, open interfaces with high-levelapplication services such as, interface icons (small), onlineordering (a business component)

Components can be distributed dynamically for reuse acrossmultiple applications and heterogeneous computingplatforms.


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Managerial Considerations

The traditional SDLC approach often works well for largeprojects with well-defined requirements, where there is not alot of time pressure.

Prototyping requires effective management to make sure thatthe iterations of prototyping do not continue indefinitely.

RADmay be less appropriate than conventional programminglanguages for larger projects, or those with a lot of real-time

processing.JAD is easy for senior management to understand, yet it isdifficult and expensive to get all people in the same place at thesame time.


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Managerial Considerations ( cont.)

A component-based application architecture providesseveral business benefits, but the execution of component-based development requires special training and skill.

End-user development is also a possibility for largerprojects whose priorities are not high enough to lead to atimely response from the central IS unit.

Outsourcing should always be considered by large andcomplex systems with a significant risk of failure, yet thedisadvantages should be reviewed carefully.


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WHY SOFTW ARE PR OJE CTS FA IL


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Most Pro jects Start wit h Optimism

... and sometimes evenwild enthusiasm


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Cause: Inadequate Engineeringand Management Practices

... and too often wedo not look to the futureto guide our actions today .


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Background

Software failures are common in both large commercial projectsand government projects.

Organizations do not routinely collect data on their softwarecosts, schedules, or quality.

The material cited herein is based on public domainpublications and past DoD studies.


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A Survey of 1,500 Software Pro jects

L ate andover budget

Averagecost growth

exceeds 89%

Projectscanceledbeforecompletion

Software projectscompleted on timeand on budget

The average final product contains 61% of the originallyspecified features.

16%

31%

53%

Ref: CHAOS Study, Standish Group, Summer 1996, 1999.


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One Common C h aracteristic:Too Muc h Effort Spent on R ework

State of Practice

* Ref: Standish Group, www.standishgroup.com, 1996, 1999.a

Development Integration and System Test

60 - 80 % of effort and cost*

too much effort, time, and cost spent on removing defects

found during testing (software quality is important!)


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Top 10 R easons for Software Failures

1. Insufficient senior staff and/or inexperienced softwareengineering cadre

2. Acquirers and developers lack experience working as ateam

3. Inadequate contract incentives to encourage use of modern software engineering practices

4. Inadequate process emphasis

5. Inadequate project management methodology


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Top 10 R easons for Software Failures

6. Software objectives are not fully understood or specified;they change frequently (and grow) during the project

7. Size matters large projects get into trouble more frequentlythan smaller ones do

8. Inadequate planning and estimating

9. Software issues are considered too late in the system-development process

10. Technology used is new to the organization


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Defense Science Board (DS B) R ecommendations*

1. Collect, disseminate and employ best practices

2. Stress software past performance, consider

non-traditional sources

3. Restructure contract incentives

4. Develop serious training and education

5. Initiate independent expert reviews

6. Strengthen the technology base*

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Topic9 SDLC