Systems Analysis and Design by Keval

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Chapter 1

Introduction to SystemsDesign and Analysis

Systems Analysis and Design

Kendall and Kendall

Sixth Edition



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Readings & Major Topics

Readings

Chapter 1 (p. 1) in the textbook

Major Topics

Information systems

SDLC (Systems Development Life Cycle)

Phases of analysis and design

CASE tools



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Information

What is information?

Domain dependent

Facts, concepts, or instructions; any sort of knowledgeor supposition which can be communicated.

Organizational resource

Must be managed as carefully as other resources (e.g.,raw material, labor)

Costs are associated with information processing

Production, distribution, security, storage, retrieval, …

Information processing must be managed to take fulladvantage of its potential



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Systems Analysis & Design

Goals Analyze data input, processing or

transforming data, data storage, andinformation output within the context of aparticular business

Analyze, design, and implement

improvements in the functioning of abusiness via the use of computerizedinformation systems



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How can we Analyze and DesignSystems?

Intuitive approach

Pros and Cons?

Systematic approach

Pros and cons?



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Systems Analysis and Design inthis Course

Systematic approach to identifyingproblems, opportunities, and objectives;

analyzing the information flows inorganizations; and designingcomputerized information systems to

solve a problem


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Systems Analyst

Performs systems analysis and design

Assesses how businesses function byexamining the inputting and processingof data and the outputting of information with the intent of improving

organizational processes



Different Types of Systems Analysts

Two major types

Outside consultants to businesses

Hired specifically to address information systems issues

within a business

Supporting experts (within a business you are regularlyemployed)

Not a full-blown systems project, but rather entails a smallmodification or decision affecting a single department

Your role as a systems analyst: agent of change

Catalyst for change (i.e., improvements to the businessthat can be done via information systems)



Interactions of a Systems Analyst

A systems analyst interacts with usersat different levels in the organization

User managersOperations workers

Systems managers

Systems designers

Programmers

….



Qualities of a Systems Analyst

Analysts are problem solvers.

Communication skills

Analysts must be ethical with users and customers ACM‟s (Association of Computing Machinery) code of

ethics

…

respect the privacy of others

Give comprehensive and thorough evaluations of computer systems and their impacts, including

analysis of possible risks

…..



Systems Development LifeCycle (SDLC)

SDLC is a systematic approach tosolving business problems

It is divided into seven phasesEach phase has unique activities

A phase is never accomplished as a

separate phaseSeveral activities can occur simultaneously

Activities may be repeated



Phase 1: Identifying problems,opportunities, and objectives

Identifying

Problems: don‟t want to address the wrong

problemsOpportunities: situations that can be improved

Objectives: how can the organization reach itsobjectives via computerized IS

Personnel involved

Analyst

User managers

Systems managers



Phase 2: Determining InformationRequirement

Understand how the business functions and havecomplete information on the people, goals, data, andprocedures

Interview management, operations personnel

Gather systems/operating documents

Use questionnaires

Observe the system and personnel involved

Learn the details of the current system functions:who (people involved), what (business activities),where (environment in which the work takes place),when (timing), how (procedures), and the why (why

is it done this way)



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Phase 2: Determining InformationRequirement (cont‟d)

Personnel involved

Analyst

User managers

Operations workers

Systems managers

Information Analyst (phases 1 and 2)



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Phase 3: Analyzing SystemsNeeds

Analyzing system needs

Create data flow diagrams

Document procedural logic for data flow diagramprocesses

Complete the data dictionary

Analyze structured decisions

Make semistructured decisions (decisions takenunder risk)

Prepare and present the system proposal

Recommend the optimal solution to management



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Phase 3: Analyzing SystemsNeeds (cont‟d)

Analyst makes recommendations tomanagement

Management decide whether to continueor not

Personnel involved Analyst

User managers

Systems managers



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Phase 4: Designing theRecommended System

Accomplish the logical design of theinformation system

Design the user interfaceDesign output

Design input

Design files and/or database

Design control and backup procedures Produce decision trees or tables

Produce program specifications



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Phase 4: Designing theRecommended System (cont‟d)

Personnel involved

Analyst

System designer

User managers

Operations workers

Systems managers



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Phase 5: Developing andDocumenting Software

Develop any original software that is needed

Design computer programs using structure

charts, Nassi-Schneiderman charts, andpseudocode

Walkthrough program design

Write computer programsDocument software with help files, procedure

manuals, and Web sites with Frequently AskedQuestions (FAQs)



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Phase 5: Developing andDocumenting Software (cont‟d)

Personnel involved

Analyst

System designer

Programmers

Systems managers



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Phase 6: Testing and Maintainingthe system

Testing and maintaining the system

Test and debug computer programs

Test the computer system Enhance system

Personnel involved

Analyst

System designer

Programmers

Systems management



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System Maintenance

Maintenance: starts in phase 6 butcarried out routinely throughout the life

of the ISSystem maintenance isRemoving undetected errors, and

Enhancing existing softwareTime spent on maintenance typically

ranges from 48-60 percent of total time



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System Enhancements

Systems are enhanced for the followingreasons:

Adding additional features to the system

Business and governmental requirementschange over time

Technology, hardware, and software arerapidly changing



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Phase 7: Implementing andEvaluating the System

Implementing and evaluating the system

Plan conversion from the old system to the

new oneTrain users

Purchase and install new equipment

Convert files

Install system

Review and evaluate system: whether theintended users are indeed using the system



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Phase 7: Implementing andEvaluating the System (cont‟d)

Personnel involved

Analyst

System designer

Programmers

User managers

Operations workersSystems managers



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CASE Tools

Computer-Aided Software Engineering (CASE)

CASE tools are automated, microcomputer-basedsoftware packages for systems analysis anddesign

Four reasons for using CASE tools are:

To increase analyst productivity

Facilitate communication among analysts and users

Providing continuity between life cycle phases

To assess the impact of maintenance



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CASE Tool Categories

CASE tools may be divided into severalcategories

Upper CASE (also called front-end CASE)tools, used to perform analysis and design

Lower CASE (also called back-end CASE).

These tools generate computer languagesource code from CASE design

Integrated CASE, performing both upperand lower CASE functions



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Upper CASE

Upper CASE tools

Create and modify the system design

Store data in a project repository

The repository is a collection of records,elements, diagrams, screens, reports, and

other project informationThese CASE tools model organizational

requirements and define systemboundaries



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Lower CASE

Lower CASE tools generate computersource code from the CASE design

Source code may usually be generatedin several languages



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Lower CASE: Advantages of Generating Code

Time to develop new systems decreases

The time to maintain generated code is less

than to maintain traditional systemsComputer programs may be generated in more

than one language

CASE design may be purchased from third-

party vendors and tailored to organizationalneeds

Generated code is free from program coding

errors



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Reverse Engineering

Reverse engineering is generating theCASE design from computer program

codeSource code is examined, analyzed, and

converted into repository entities

Uses Computer-Assisted Reengineering(CARE) software



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Reverse Engineering Produces

Depending on the tool set used:

Data structures and elements, describing

the files, records, and fieldScreen designs, if the program is online

Report layouts for batch programs

A structure chart showing the hierarchy of the modules in the program

Database design and relationships



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Advantages of ReverseEngineering

It has the following advantages:

Reduced system maintenance time

Program documentation is produced forloosely documented programs

Structured programs may be generated fromunstructured, older programs

Future system maintenance is easier toimplement

Unused portions of programs may be

eliminated



Chapter 2

Information Gathering:Interactive Methods


Kendall and Kendall

Sixth Edition



4-35


Readings

Chapter 4 in the textbook (p. 89)

Major Topics

Interviewing techniques

Joint Application Design (JAD)

Questionnaires



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Information Gathering in SDLC

Phase 1 Identifyingproblems, opportunities,

and objectives

Phase 2 Determining

information requirements

Phase 3 Analyzingsystems needs

Phase 4 Designing the

recommended system

Phase 5 Developing anddocumenting software

Phase 6 Testing andmaintaining the system

Phase 7 Implementing

and evaluating thesystem



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Information Gathering:Two Approaches

Interactive: talking with and listening topeople in the organization through a series of carefully composed questions Example: interviewing

Unobtrusive: do not require the same degreeof interactivity between analysts and users Example: observing

Our focus: Interactive methods Interviewing JADQuestionnaires



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Interviewing

Important method for collecting data oninformation system requirements

Directed conversation with a specific purposethat uses Q&A format

Reveals information about

Interviewee opinions

Feelings about the current state of the system

Organizational and personal goals

Informal procedures



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Planning the Interview

Five steps in planning the interview are

Reading background material

Establishing interview objectives

Deciding whom to interview

Preparing the interviewee

Deciding on question types and structure



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Before the Interview

Contact the interviewee and confirm theinterview

Dress appropriately

Arrive a little early

Affirm that you are present and readyto begin the interview



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Recording the Interview

Interviews can be recorded with taperecorders or notes

Audio recording should be done withpermission and understanding

Ad t f A di



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Advantages of AudioRecording the Interview

Providing a completely accurate record of

what each person saidFreeing the interviewer to listen and

respond more rapidly

Allowing better eye contact and betterrapport

Allowing replay of the interview for otherteam members

Di d t f A di



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Disadvantages of AudioRecording the Interview

Possibly making the interviewee nervous

and less apt to respond freelyDifficulty in locating important passages on

a long tape

N t T ki D i



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Note Taking DuringInterviews: Pros and Cons

Pros

Keeping the interviewer alert

Aiding recall of important interview trendsShowing interviewer interest in the interview

Cons

Losing vital eye contactLosing the train of conversation

Causing excessive attention to facts and less

attention to feelings



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Beginning the Interview

Shake hands

Remind them of your name and why

you are there

Take out note pad or tape recorder

Make sure tape recorder is working

correctly



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Opening Questions

Start with pleasant conversation

Listen closely to early responses

Pick up on vocabulary

Look for metaphors

“The accounting department is a zoo”

“We‟re one big family here”



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During the Interview

The interview should not exceed 45minutes to one hour

Make sure that you are understandingwhat the interviewee is telling you

Ask for definitions if needed



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Closing the Interview

Always ask “Is there anything else thatyou would like to add?”

Ask whom you should talk with next

Set up any future appointments

Thank them for their time and shake

hands



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Interview Report

Write as soon as possible after theinterview

Provide an initial summary, then moredetail

Review the report with the respondent



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Question Types

There are two basic types of interviewquestions:

Open-endedClosed



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Open-Ended Questions

Allow interviewees to respond how theywish, and to what length they wish

E.g.: Once the data is submitted via the Website, how is it processed?

Appropriate when the analyst is interestedin breadth and depth of reply

Advantages of Open Ended



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Advantages of Open-EndedQuestions

Putting the interviewee at ease

Allowing the interviewer to pick up on the

interviewee's vocabularyProviding richness of detail

Revealing avenues of further questioning

that may have gone untapped Allows more spontaneity

Useful if the interviewer is unprepared

Disadvantages of Open Ended



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Disadvantages of Open-EndedQuestions

May result in too much irrelevant detail

Possibly losing control of the interview

May take too much time for the amount of useful information gained

Potentially seeming that the interviewer is

unpreparedPossibly giving the impression that the

interviewer is on a "fishing expedition”



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Closed Interview Questions

Limit the number of possibleresponses

E.g.: On average, how many calls does thecall center receive monthly?

Appropriate for generating precise,reliable data which is easy to analyze

Advantages of Closed



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Advantages of ClosedInterview Questions

Saving interview time

Easily comparing interviews

Getting to the pointKeeping control of the interview

Covering a large area quickly

Getting to relevant data

Disadvantages of Closed



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Disadvantages of ClosedInterview Questions

Boring for the interviewee

Failure to obtain rich detailMissing main ideas

Failing to build rapport between

interviewer and interviewee



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Bipolar Questions

Questions that may be answered with a „yes‟ or „no‟ or „agree‟ or „disagree‟

E.g.: Do you want to receive a printout of your account status every month?

E.g.: Do you agree or disagree thatecommerce on the Web lacks security?



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Probing Questions

Elicit more detail about previous questions

The purpose of probing questions is

To get more meaning To clarify

To draw out and expand on the interviewee'spoint

E.g.: Please give an illustration of the securityproblems you‟re experiencing with your onlinesystems?

Tradeoffs: Open ended and



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Tradeoffs: Open-ended andClosed Questions

Reliability of data

Efficient use of time

Precision of data Breadth and depth

Interviewer skill required

Ease of analysis



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Question Pitfalls

Leading questions: imply an answer

Tend to guide interviewees into responses apparentlydesired by the interviewer

Should be avoided to reduce bias and improve reliabilityand validity

E.g.: You agree with other managers that inventorycontrol should be computerized, don‟t you?

Double-barreled questions: two questions in one Interviewees may answer only one question, leading to

difficulties in interpretation

E.g.: What decisions are made during a typical day and

how do you make them?



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Question Sequencing

There are three basic ways of structuring interviews:

PyramidFunnel

Diamond



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Pyramid Structure

Begins with very detailed, often closedquestions

Expands by allowing open-endedquestions and more generalizedresponses

Is useful if interviewees need to bewarmed up to the topic or seemreluctant to address the topic



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Funnel Structure

Begins with generalized, open-endedquestions

Concludes by narrowing the possibleresponses using closed questions

Provides an easy, non-threatening way

to begin an interviewIs useful when the interviewee feels

emotionally about the topic



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Diamond Structure

A diamond-shaped structure begins in avery specific way

Then more general issues are examinedConcludes with specific questions

Is useful in keeping the interviewee's

interest and attention through a varietyof questions



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Joint Application Design (JAD)

Can replace a series of 1-on-1 interviews

Allows the analyst to accomplish

requirements analysis and design the userinterface with the users in a group setting

Systems analysts (SAs): passive role

SAs Should be present

May give expert opinions about anydisproportionate costs of solutions



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Topics Discussed in JAD

Requirements analysis and user interfacedesign But could be used at any appropriate phase of

SDLC

Address topics such as Planning, receiving, receipt processing/tacking,

monitoring and assigning, processing, recording,

sending, and evaluating For each topic, ask:

Who, what, how, where, and why



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JAD Personnel

Analysts

Users, executives, … (8 to 12)

Observers (technical experts) A scribe: write down everything

A session leader

Senior person: visible symbol of organizationalcommitment

May be outside management consultant



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Preparing a JAD Session

Two-to-four-day sessions offsite

If possible, away from the organization, in

comfortable surroundingsMinimize the daily distractions and

responsibilities of the participants‟ regular work

Use of group decision support facilities (e.g.,

networked computers, projection system, …) Make use everybody will be able to attend

Orientation meeting (1/2 day) a week before the workshop



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When to Use JAD

Users are restless and want somethingnew

The organizational culture supports jointproblem-solving behaviors

Analysts forecast an increase in thenumber of ideas using JAD

Personnel may be absent from their jobsfor the length of time required



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Benefits of JAD

Time is saved, compared with traditional

interviewing (15%)Rapid development of systems

Improved user ownership of the system

Creative idea production is improved



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Drawbacks of Using JAD

Requires a large block of time be availablefor all session participants

If preparation is incomplete, the sessionmay not go very well

If the follow-up report is incomplete, thesession may not be successful

The organizational skills and culture maynot be conducive to a JAD session



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Questionnaires

Also called Surveys Respondent: person answering a

questionnaire (or survey)

Useful in gathering information from keyorganization members about Attitudes: what people say they want (in the new

system)

Beliefs: what people think is actually true Behaviors: what organizational members do Characteristics: properties of people or things



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When to Use Questionnaires

Organization members are widely dispersedMany members are involved with the project Exploratory work is needed: quantify what was

found in interviewsHow widespread or limited an opinion expressed in aninterview really is

Problem solving prior to interviews is necessaryRaise important issues before interviews are scheduled

May be used in conjunction with interviewsFollow-up unclear questionnaire responses withinterviews

Design questionnaires based on what was discovered ininterviews



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Question Types

Questions are designed as either

Open-ended

Try to anticipate the response you will get

Well suited for getting opinions

Useful in explanatory situations

Useful when it is impossible to list effectively all possibleresponses to a question

ClosedUse when all the options may be listed

When the options are mutually exclusive

Open-Ended vs.



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Open Ended vs.Closed Questions

Open-ended Closed

Slow Speed of completion FastHigh Exploratory nature Low

High Breadth and depth Low

Easy Ease of preparation Difficult

Difficult Ease of analysis Easy



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Questionnaire Language

Simple: use the language of respondents wheneverpossible

Specific and short questionsFree of bias

Not patronizing: avoid low-level language choices

Technically accurate

Right question to the right person: addressed tothose who are knowledgeable

Appropriate for the reading level of the respondent



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Using Scales in Questionnaires

Assigning numbers or other symbols to anattribute/characteristic for the sake of

measuring that attribute/characteristic

Devised to have respondents act as judges

for the subject of the questionnaire



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Measurement Scales

There are four different forms of measurement scales:

NominalOrdinal

Interval

Ratio



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Nominal Scales

Nominal scales are used to classify

things into categories

What type of software do you use the most?

1 = Word Processor

2 = Spreadsheet3 = Database

4 = An Email Program



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Ordinal Scales

Allow classification

Ordinal scales also imply rank orderingThe support staff of the Technical Support Group is:

1. Extremely Helpful

2. Very Helpful

3. Moderately Helpful

4. Not Very Helpful

5. Not Helpful At All



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Interval Scales

An interval scale is used when the

intervals are equalThere is no absolute zero

How useful is the support given by the Technical Support Group?

NOT USEFUL EXTREMELY

AT ALL USEFUL

1 2 3 4 5



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Ratio Scales

The intervals between numbers areequal

Ratio scales have an absolute zeroApproximately how many hours do you spend on the Internet daily?

0 2 4 6 8



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Guidelines for Using Scales

Use a ratio scale when intervals areequal and there is an absolute zero

Use an interval scale when intervals areequal but there is no absolute zero

Use an ordinal scale when the intervals

are not equal but classes can be rankedUse a nominal scale when classifying

but not ranking



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Validity and Reliability

Reliability: Consistency in response

Getting the same results if the samequestionnaire was administered againunder the same conditions

Validity: Degree to which the questionmeasures what the analyst intends tomeasure

Problems Associated With Poorly



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Problems Associated With PoorlyConstructed Scales

Leniency: caused by easy raters

Central tendency: respondents rate

everything as averageHalo effect: impression formed in one

question carries into the next question



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Questionnaire Format

Allow ample white space

Allow enough space for responses to betyped for open-ended questions

Ask respondents to clearly mark theiranswers

Be consistent in style



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Order of Questions

Most important questions go first

Similar topics should be clustered

together

Controversial questions should bepositioned after less controversial

questions

Methods of Administering



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gQuestionnaires

Convening All concerned respondentstogether at one time

Personally administering the questionnaire

Allowing respondents to self-administer thequestionnaire

Mailing questionnaires: supply deadlines,instructions, and return postage

Administering over the Web or via email



Chapter 3Data Flow Diagrams


Kendall and KendallSixth Edition



90


ReadingsChapter 7 in the textbook (p. 191)

Major TopicsData flow diagram symbols

Data flow diagram levels

Creating data flow diagramsPhysical and logical data flow diagrams

Partitioning



91

Data Flow Diagrams in SDLC

Phase 1 Identifying

problems, opportunities,

and objectives

Phase 2 Determining




recommended system

Phase 5 Developing and

documenting software

Phase 6 Testing and

maintaining the system


and evaluating the

system



92

Data Flow Diagrams (DFDs)

One of the main methods available foranalyzing data-oriented systems

DFD: a graphical representation of datamovement through the organizationProcesses

Transforming of data as it moves through a

variety of processes within the enterprise

Inputs/outputs

Data storage



93

Why DFDs?

Freedom from committing to the technical

implementation too earlyUnderstanding of the interrelationships of

systems and subsystems

Communicating current system knowledgeto users



94

Basic Symbols in DFDs

A double square for an external entity--a

source or destination of data An arrow for movement of data from one

point to another

A rectangle with rounded corners for theoccurrence of transforming process

An open-ended rectangle for a data store



95

External Entities

Represent people or organizationsoutside of the system being studied

Shows the initial source and finalrecipient of data and information

Should be named with a noun,

describing that entityCustomer



96

External Entities (cont‟d)

External entities may be

A person, such as CUSTOMER or STUDENT

A company or organization, such as BANK or SUPPLIER

Another department within the company,such as ORDER FULFILLMENT

Another system or subsystem, such as theINVENTORY CONTROL SYSTEM



97

Processes

Represent either:

A whole system

A subsystemWork being done, an activity

Names should be in the form verb-

adjective-nounThe exception is a process that represents

an entire system or subsystem

1

Add New

Customer

2

CustomerInquiry

Subsystem



98

Data Stores

Name with a noun, describing the data

Data stores are usually given a unique

reference number, such as D1, D2, D3 Include any data stored, such as:

A computer file or database

A transaction file A set of tables

A manual file of records

D1CustomerMaster

New Customer



99

Data Flow

Shows the data about a person, place,or thing that moves through the system

Names should be a noun that describesthe data moving through the system

Arrowhead indicates the flow direction

Use double headed-arrows only when aprocess is reading data and updatingthe data on the same table or file

Customer Record



100

Data Flow Diagram Levels

Data flow diagrams are built in levels

The top level is the Context level DFD

Each process may explode to a lowerlevel

The lower level diagram number is the

same as the parent process numberProcesses that do not create a child

diagram are called primitive

Data Flow Diagram Levels



101

g(cont‟d)

Different levels of DFDs

One (1) Context level DFD

One (1) Diagram 0One or more Child Diagrams



102

Context Level DFD

Contains only one process, representing theentire system to be designed/analyzed

Highest-level diagram

Overview including basic inputs, the generalsystem, and basic outputs

The process is given the number zero (0)

Includes all external entities as well as majordata flow to and from them

The diagram does not contain any data stores



103

Diagram 0

Diagram 0 is the explosion of thecontext level diagram (i.e., process 0)

Should include up 9 processes Any more will result in a cluttered diagram

Processes are numbered with an integer

The major data stores and all externalentities are included in Diagram 0



104

Child Diagrams

Each process on diagram zero may be (if notprimitive) exploded to create a child diagram

Each process on a lower-level diagram maybe (if not primitive) exploded to createanother child diagram

A diagram found below Diagram 0 is given

the same number as its parent processProcess 3 in Diagram 0 would explode to

Diagram 3



105

Child Diagrams (cont‟d)

Each process is numbered with the parentdiagram number, a period, and a unique childnumber

Examples are:On Diagram 3, the processes would be

numbered 3.1, 3.2, 3.3 and so on

3.2 on Diagram 3, a child of process 3

5.2.7 on Diagram 5.2, a child of process 5.2

3.2

Edit

Customer

5.2.7

CalculateCustomerDiscount



106


External entities are usually not shownon the child diagrams below Diagram 0

If the parent process has data flowconnecting to a data store, the childdiagram may include the data store as

well



107


A lower-level diagram may contain data storesnot shown on the parent process, such as

A file containing a table of information (such asa tax table)

A file linking two processes on the child diagram

Minor data flow, such as an error line, may be

included on a child diagramHandling of exceptions is generally ignored for

the first two levels



108


Vertical Balancing rule

A child diagram cannot produce output or

receive input that the parent process doesnot also produce or receive

Must be respected while designingDFDs



109


An interface data flow is data that areinput or output from a child diagram

that matches the parent diagram dataflow

Processes that do not create a child

diagram are called primitive processesLogic is written for these processes (will be

discussed in another chapter)



110

Data Flow Diagram Errors

A process with only input data flow or

only output data flow from it

AddNewCustomer

1

AddNewCustomer

2



111

Data Flow Diagram Errors (cont‟d)

Data stores or external entities are connecteddirectly to each other, in any combination

Customer D1 Customer

Vendor D2 Vendor Master



112


Incorrectly labeling data flow or objects

Examples are

Labels omitted from data flow or objects

Data flow labeled with a verb

Processes labeled with a noun

Too many processes on a data flowdiagram

Nine is the suggested maximum



113


Omitting data flow from the diagram

Unbalanced decomposition between a

parent process and a child diagramThe data flow in and out of a parent

process must be present on the childdiagram



114

Guidelines for Developing DFDs

Create the context level diagram, includingall external entities and the major dataflow to or from them

Create Diagram 0 by analyzing the majoractivities within the context process

Include the external entities and major

data stores

Create a child diagram for each complexprocess on Diagram 0

Guidelines for Developing



115

p gDFDs (cont‟d)

Detailed DFDs (child or Diagram 0) may bedeveloped by

Making a list of business activities

Analyzing what happens to an input data flowfrom an external entity

Analyzing what is necessary to create an outputdata flow to an external entity

Examining the data flow to or from a data store

Unclear areas of a data flow diagram should benoted and investigated

E t D i DFD



116

Event Driven DFDs

An input flow from an external entity iscalled a trigger

It starts processesEvents are activities that happen within

the system

E t D i DFD ( t‟d)



117

Event Driven DFDs (cont‟d)

Another approach used to create a dataflow fragment

Analyze events, which are summarized in anevent table

Events are either

External, coming from outside the system, orTemporal, which occur at fixed times

E t T bl



118

Event Tables

An event table is used to create a dataflow diagram by analyzing each event

and the data used and produced by theevent

Every row in an event table represents

a unique activity and is used to createone process on the data flow diagram

DFD P i



119

DFD Progression

The progression of creating DFDs is

Create a logical DFD of the current system

Next add all the data and processes not inthe current system which must be presentin the new system

Finally derive the physical data flowdiagram for the new system

L i l DFD



120

Logical DFDs

Logical data flow diagrams show howthe business operates

Represent features that would exist nomatter what the physical means of doing business are.

Processes that would exist regardless of the type of system implemented

L i l DFD Ad t



121

Logical DFDs Advantages

Better communication with users

More stable systems, since the design is

based on a business framework Increased understanding of the business

by analysts

Elimination of redundancy

Ph i l DFD



122

Physical DFDs

Show how the system operates or how the newsystem will be implemented

Physical DFDs include

Clarifying which processes are manual/automatic

Describing processes in greater detail

“Sequencing processes” to rearrange the order of records

“Validation processes” for ensuring accurate data input

Intermediate data stores

Actual document and file names

Controls to ensure accuracy and completeness

CRUD M t i



123

CRUD Matrix

Physical DFDs include processes foradding, reading, changing, and deleting

recordsCRUD is an acronym for Create, Read,

Update, Delete

A CRUD matrix shows which processesadd, read, update, or delete master filerecords

Pa titioning



124

Partitioning

Process of analyzing a DFD and derivinga series of manual procedures and

computer programs A dashed line is drawn around a group

of processes that are included in each

computer program or manual procedure

Manual Procedures



125

Manual Procedures

Performed by people

Have manual input and manual output

Computer processing not used withmanual processes

Batch Processes



126

Batch Processes

If the data flow into and out of aprocess is entirely computer

information, the process is called abatch process

Batch processes do not require any

human intervention A job stream is several separate

programs running back-to-back, usuallya series of batch processes

User Interface



127

User Interface

A user interface represents a screen, adata entry operation, a report, or some

other means for persons to interact witha computer

It occurs when the data flow links a

manual and an automated process

Reasons for Partitioning



128

Reasons for Partitioning

Different user groups should have differentprograms

Processes that execute at different times must be in

separate programs Processes may be separated into different programs

for security

Similar tasks may be included in the same program

Several batch processes may be included in thesame program for efficiency

Several processes may be included in the sameprogram or job stream for consistency of data

Using DFDs



129

Using DFDs

Unexploded data flow diagrams are useful to identifyinformation requirements

Exploded data flow diagrams can be used forpresentation, education, and gathering feedback information from users

DFDs may be used to analyze the system to ensurethat the design is complete

DFDs are used to partition the system into programs

Data flow diagrams can be used for the systemdocumentation

Chapter 4



Chapter 4

Analyzing SystemsUsing Data Dictionaries






131


ReadingsChapter 8 in the textbook (p. 245)

Major TopicsData dictionary concepts

Defining data flow

Defining data structures

Defining elements

Defining data stores

Data Dictionaries in SDLC



132

Data Dictionaries in SDLC

Phase 1 Identifying


and objectives

Phase 2 Determining




recommended system



Phase 6 Testing and



and evaluating the

system

Data Dictionary



133

Data Dictionary

Reference work of data about data(metadata)

Main method for analyzing data flowsand data stores

Collects, coordinates, and confirms

what a specific data term means todifferent people in the organization

Reasons for Using a DataDictionary



134

Dictionary

Some reasons

Provide documentation

Eliminate redundancy

Validate the data flow diagram

Provide a starting point for developing screensand reports

Develop the logic for DFD processes

Automated dictionaries (CASE tools)

Cross-reference data items

The Repository



135

The Repository

A data repository is a large collection of project information

It includes

Information about system data

Procedural logic

Screen and report design

Project requirements and deliverables

Project management information (e.g.,delivery schedules, achievements, …)

Data Dictionary Contents



136

Data Dictionary Contents

Data dictionaries contain data about

Data flow

Data flow description formData structures

Data Elements

Element description form

Data stores

Data store description form

Data Flow Description Form



137

Data Flow Description Form

Each data flow should be defined withdescriptive information and it's

composite structure or elementsIncludes:

ID - identification number

Unique name for the data flow: shouldappear on the DFD

A general description of the data flow

Data Flow Description Form(cont‟d)



138

(cont d)

Includes:

The source of the data flow

This could be an external entity, a process, or adata flow coming from a data store

The destination of the data flow

Type of data flow, either

A record entering or leaving a file

Containing a report, form, or screen

Internal - used between processes

Data Flow Description Form(cont‟d)



139

(cont d)

Includes:

The name of the data structure or

elementsThe volume per unit time

This could be records per day or any other unitof time

An area for further comments andnotations about the data flow

Data Flow Description Form -Example



140

Example

Name Customer Order

Description Contains customer order information and is used

to update the customer master and item files and

to produce an order record.

Source Customer External Entity

Destination Process 1, Add Customer Order

Type Screen

Data Structure Order Information

Volume/Time 10/hourComments An order record contains information for one

customer order. The order may be received by

mail, fax, or by telephone.

Defining Data Structures



141

Defining Data Structures

Data structures are a group of smallerstructures and elements

An algebraic notation is used torepresent the data structure

Algebraic Notation



142

Algebraic Notation

The symbols used are

Equal sign, meaning “consists of”

Plus sign, meaning "and”

Braces {} meaning repetitive elements,also called repeating groups or tables

Brackets [] for an either/or situation

The elements listed inside are mutuallyexclusive

Parentheses () for an optional element

Repeating Groups



143

Repeating Groups

A repeating group may be A sub-form A screen or form table A program table, matrix, or array

There may be one repeating element or severalwithin the group

The repeating group may have A fixed number of repetitions

12 {Monthly Sales}Upper and lower limits for the number of

repetitions {Order Line}5

1

Structural Records



144

Structural Records

A structure may consist of elements or smallerstructural records

These are a group of fields, such as

Customer Name, Address, Telephone

Each of these must be further defined until onlyelements remain

Structural records and elements used within manydifferent systems should be given a non-system-specific name

E.g.: street, city, and zip



Logical Data Structures



146

Logical Data Structures

Data structures may be either logical orphysical

Logical data structures indicate thecomposition of the data familiar to theuser

Physical Data Structures



147

Physical Data Structures

Include elements and informationnecessary to implement the system

Additional physical elements includeKey fields used to locate records

Codes to indicate record status

Codes to identify records when multiplerecord types exist on a single file

Etc.

Data Structure Example



148

Data Structure Example

Customer Order = Customer Number +

Customer Name +

Address +

Telephone +

Catalog Number +

Order Date +{Order Items} +

Merchandise Total +

(Tax) +

Shipping and Handling +

Order Total +Method of Payment +

(Credit Card Type) +

(Credit Card Number) +

(Expiration Date)

Element Description Forms



149

Element Description Forms

Data elements should be defined withdescriptive information, length and type

of data information, validation criteria,and default values

Each element should be defined once inthe data dictionary

Element Description Forms -Attributes



150

Attributes

Element ID. This is an optional entry thatallows the analyst to build automated datadictionary entries

The name of the element, descriptive andunique

It should be what the element is commonlycalled in most programs or by the major user of the element



Element Description Forms – Attributes (cont‟d)



152

Attributes (cont d)

Whether the element is base or derived

A base element is one that has been initiallykeyed into the system

A derived element is one that is created by aprocess, usually as the result of a calculation orsome logic

Element Description Forms -Attributes (cont‟d)



153

Attributes (cont d)

The length of an element Some elements have standard lengths, such as a

state abbreviation, zip code, or telephone number

For other elements, the length may vary and theanalyst and users must decide the final length

Numeric amount lengths should be determined byfiguring the largest number the amount willcontain and then allowing room for expansion

Totals should be large enough to accommodatethe numbers accumulated into them

It is often useful to sample historical data todetermine a suitable length




154

Attributes (cont d)

Percent of data that will

Element Length fit within the length (US)

Last Name 11 98%

First Name 18 95%

Company Name 20 95%

Street 18 90%

City 17 99%




155

Attributes (cont d)

The length of an element (cont‟d)

Data Truncation

If the element is too small, the data will betruncated

The analyst must decide how this will affect thesystem outputs

If a last name is truncated, mail would usuallystill be delivered

A truncated email address or Web address isnot usable




156

Attributes (cont d)

The type of data

Numeric, date, alphabetic or alphanumeric orother microcomputer formats

Input and output formats should be included,using coding symbols:

Z – Leading Zeros or spaces

9 - Number

X - Character

X(8) - 8 characters

Etc.




157

Attributes (cont d)

Validation criteria

Discrete, meaning they have fixed values

Discrete elements are verified by checking thevalues within a program

They may search a table of codes

Continuous, with a smooth range of values

Continuous elements are checked that the datais within limits or ranges




158

Attributes (cont d)

Default value

The default value is displayed on entryscreens

Reduces the amount of keying

Comments

This might be used to indicate the formatof the date, special validation that isrequired, etc.

Data Element Example



159

Data Element Example

Name Customer Number

Alias Client Number

Alias Receivable Account Number

Description Uniquely identifies a customer that has made any business

transaction within the last five years.

Length 6Input Format 9(6)

Output Format 9(6)

Default Value

Continuous/Discrete Continuous

Type Numeric

Base or Derived DerivedUpper Limit <999999

Lower Limit >18

Discrete Value/Meaning

Comments The customer number must pass a modulus-11 check-digit test.

Data Store Description Form



160

Data Store Description Form

Data stores contain a minimal of all baseelements as well as some derived elements

Data stores are created for each different

data entity, that is, each different person,place, or thing being stored

Since a data flow may only show part of thecollective data, called the user view, you may

have to examine many different data flowstructures to arrive at a complete data storedescription

Data Store Description Form -Attributes



161

Attributes

The Data Store ID

The Data Store Name: descriptive and unique

An Alias for the file

A short description of the data store

The file type:Manual or computerized

If the file is computerized, the file formatdesignates whether the file is a database file orthe format of a traditional flat file

Data Store Description Form – Attributes (cont‟d)



162

bu ( o d)

The maximum and average number of records on the file

The growth per year

Predict the amount of disk space required

The data set name specifies the table or filename, if known

In the initial design stages, this may be leftblank

The data structure should use a name foundin the data dictionary

Data Store Description Form – Attributes (cont‟d)



163

( )

Primary and secondary keys must beelements (or a combination of elements)found within the data structure

Example: Customer Master FileCustomer Number is the primary key, which

should be unique

The Customer Name, Telephone, and Zip Codeare secondary keys

Comments

Data Store Example - Part 1



164

p

ID D1

Name Customer Master File

Alias Client Master File

Description Contains a record for each customerFile Type Computer

File Format Database

Record Size 200

Maximum Records 45,000

Average Records 42,000

Percent Growth/Year 6%

Data Store Example - Part 2



165

p

Data Set/Table Name Customer

Copy Member Custmast

Data Structure Customer Record

Primary Key Customer NumberSecondary Keys Customer Name, Telephone, Zip Code

Comments The Customer Master file records are

copied to a history file and purged if the customer has not

purchased an item within the past five years. A customer

may be retained even if he or she has not made a purchase

by requesting a catalog.

Data Dictionary and Data FlowDiagram Levels



166

g

Data dictionary entries vary according to the levelof the corresponding DFD

Data dictionaries are created in a top-down

manner Whole structures, such as the whole report or screen, are

used on the top level of the DFD

Data structures are used on intermediate-level DFD

Elements are used on lower-level data flow diagrams Data dictionary entries may be used to validate

parent and child DFD level balancing

Creating Data Dictionaries



167

g

1. Information from interviews and JADsessions is summarized on Input andOutput Analysis Forms

This provides a means of summarizingsystem data and how it is used

2. Each structure or group of elementsis analyzed




168

g

3. Each element should be analyzed byasking the following questions:

A. Are there many of the field?If the answer is yes, indicate that the field is a

repeating field using the { } symbols

B. Is the element mutually exclusive of

another element?If the answer is yes, surround the two fields

with the [ | ] symbols




169

g

C. Is the field an optional entry oroptionally printed or displayed?

If so, surround the field with parenthesis ( )

4. All data entered into the system mustbe stored

Create one file or database file for each

different type of data that must be stored Add a key field that is unique to each file

Determining Data StoreContents



170

Data stores may be determined byanalyzing data flows

Each data store should consist of elements on the data flows that arelogically related, meaning they describethe same entity

Maintaining the DataDictionary



171

y

To have maximum power, the datadictionary should be tied into otherprograms in the system

When an item is updated or deletedfrom the data dictionary it isautomatically updated or deleted fromthe database

Using the Data Dictionary



172

g y

Data dictionaries may be used to

Generate computer program source code

Create reports, screens, and forms Analyze the system design for completion

and to detect design flaws

Creating Reports, Screens,Forms



173

To create screens, reports, and forms

Use the element definitions to create fields

Arrange the fields in an aestheticallypleasing screen, form, or report, usingdesign guidelines and common sense

Repeating groups become columns

Structural records are grouped together onthe screen, report, or form

Data Dictionary Analysis



174

The data dictionary may be used in conjunction with thedata flow diagram to analyze the design, detecting flawsand areas that need clarification

Some considerations for analysis are

All base elements on an output data flow must be presenton an input data flow to the process producing the output

Base elements are keyed and should never be created by aprocess

A derived element should be output from at least one

process that it is not input into The elements that are present on a data flow into or coming

from a data store must be contained within the data store

Chapter 5Describing Process



g

Specifications and StructuredDecisions






176

Readings Chapter 9 in the textbook (page 283)

Major TopicsProcess specifications

Decision tables

Other Types of SpecificationsStructured English

Decision trees

Process Specification in SDLC



177

Phase 1 Identifying


and objectives

Phase 2 Determininginformation requirements

Phase 3 Analyzing

systems needs


recommended system



Phase 6 Testing and



and evaluating the

system

Process Specifications



178

Process specifications (minispecs) arecreated for primitive processes and

some higher level processes on a DFDDocumenting and analyzing the logic of

structured decisions

Structured English

Decision trees

Decision tables

Goals of Creating ProcessSpecifications



179

Reduce process ambiguity

Obtain a precise description of what isaccomplished

Validate the system design, including dataflow diagrams and the data dictionary

No Process Specifications For



180

Physical input and/or output processes

Processes that represent simple datavalidation

Processes for which prewritten codealready exists

Process Logic



181

Process descriptions may exist on a formor within a CASE tool repository

Process logic may be represented as

Structured English

A decision table

A decision tree

Any combination of the above

Process Specification Format



182

The process number, which must matchthe process ID on the data flow diagram

This allows an analyst to work or review any

process and easily locate the DFD containingthe process

The process name, the same as displayswithin the process symbol on the DFD

A brief description of what the processaccomplishes

Process Specification Format(cont‟d)



183

A list of input and output data flow, usingthe names found on the data flow diagram

Data names used in the formulae or logic

should match the data dictionary, forconsistency and good communication

An indication of the type of process

Batch, online or manual

All online processes require screen designs

All manual processes should have well-definedprocedures for employees performing theprocess tasks

Process Specification Format(cont‟d)



184

If the process has prewritten code for it,include the name of the subprogram orfunction

A reference to further information, such asa structured English description, a decisiontable or tree depicting the logic

List any unresolved issuesThese form the basis of the questions used for

a follow-up interview

Process Specification ExamplePart 1



185

Number 1

Name Add Customer Order

Description Key and add the Customer Order.

The order should be edited for correct information.Customer and Item master files are updated.

Input Data Flow

Customer Order Form from the CustomerCustomer Record from data store D1, Customer Master File

Item Record from data store D2, Item Master File

Process Specification ExamplePart 2



186

Output Data Flow

Pending Order to data store D3, Order File

Backordered Item Record to the Inventory Control Department

Updated Customer and Item records

Type of process Online

Decision Tables



187

Decision tables provide a way toexamine, describe, and documentdecisions using a table

They are used to

Describe the conditions

Identify possible decision alternatives

Indicate actions should be performed, and

Describe actions

Decision Tables



188

Decision tables help analysts ensurecompleteness and accuracy

Four main problems that can occur indeveloping decision tables

Incompleteness

Impossible situations

Contradictions

Redundancy

Parent Process Specifications



189

If a process explodes to a childdiagram, the process becomes a controlmodule when the computer programrepresenting the process is written

The logic of the process shows thesequence that the child diagram

processes must be executed in

Program Process Specification



190

All the process specifications areconsolidated for a computer programand are included in the specificationpacket given to the computerprogrammer

Since they are developed for one

process, the logic is easier tounderstand

Horizontal Balancing



191

Horizontal balancing means that alloutput data flow must be either oninput data flow or described in theprocess logic

It is used to verify that each processhas the required data dictionary entries

defined and the formulas and logicnecessary to produce the output

Rules for Horizontal Balancing



192

Rules for horizontal balancing are

All base elements on an output data flowmust be present on an input data flow

All derived elements on an output dataflow must be either

Present on an input data flow, or

Created by the process



Chapter 7Designing Databases



Database Design in SDLC



194

Phase 1 Identifying


and objectives

Phase 2 Determininginformation requirements

Phase 3 Analyzing

systems needs


recommended system



Phase 6 Testing and



and evaluating the

system




195

Readings Chapter 13 in the textbook (page 443)

Major TopicsDatabases

ER Model

Relational Model

NormalizationKey design

Objectives of EffectiveDatabases



196

Ensuring that data can be shared among users fora variety of applications

Maintaining data that are both accurate andconsistent

Ensuring all data required for current and futureapplications will be readily available

Allowing the database to evolve and the needs of the users to grow

Allowing users to construct their personal view of the data without concern for the way the data arephysically stored

Metadata



197

Metadata is the information thatdescribes data in the database

Used to help users understand the formand structure of the data

Also called “schema” in databases

Entity-Relationship (ER) Concepts



198

Entities are objects or events for whichdata is collected and stored

person, place, thing, event, unit of time, …

Relationships are associations betweenentities

Entities



199

A distinct collection of data for oneperson, place, thing, or event

Customer

Attributes, Records, and Keys



200

Attributes are a characteristic of anentity, sometimes called a field Also called data item

Records are a collection of data itemsthat have something in commonInstance of an entity

Keys are data items in a record used toidentify the record

Keys



201

Primary key, unique for the record

Secondary key, a key which may not beunique

Concatenated key, a combination of two ormore data items for the key

Foreign key, a data item in one record that

is the key of another record

Entity Subtype



202

An entity subtype represents data (fields)about an entity that may not be found onevery instance of an entity

Preferred customers may have special fieldscontaining discount information

Eliminates null fields

Preferred

Customer

Attributive Entity



203

Attributive Entity - describes attributes,especially repeating elements

Attributive entities tables, table files ordatabase code tables

Book

Subject

Relationships



204

Relationships may be

One-to-one

One-to-many

Many-to-many

A single vertical line represents one

A circle represents zero or none A crows foot represents many

Relationships



205

Many One

Many NoneO

Ordinality



206

The ordinality is the minimum numberthat can occur in a relationship

If the ordinality is zero, it means that itis possible to have none of the entity

O OrderItem

Self-Join



207

A self-join is when a record has arelationship with another record on the

same entityStudent partners with another student on a

project

Associative Entity



208

Associative Entity - links two entities

An associative entity can only exist between twoentities

The relationship line between a many-to-manyrelationship becomes an associative entity,sometimes called a composite entity or gerund

OrderItem

Associative Entity Connections



209

Each entity end has a “one” connection

The associative entity has a “many”

connection on each side

Associative Entity Keys



210

The key fields for the associative entityare

The primary key for each “one” end is aforeign key on the associative entity

Both foreign keys concatenated togetherbecome the primary key

ER Diagram and Record Keys



211

The ER diagram may be used todetermine record keys

When the relationship is one-to-many, the

primary key of the file at the one end of the relationship should be contained as aforeign key on the file at the many end of the relationship

A many-to-many relationship should bedivided into two one-to-many relationshipswith an associative entity in the middle

Databases



212

A database is intended to be shared bymany users

There are three structures for storingdatabase files:

Hierarchical database structures

Network database structures

Relational database structures

Normalization



213

Normalization is the transformation of complex user views and data to a set of smaller, stable, and easily maintainable

data structuresNormalization creates data that are

stored only once on a file

The exception is key fieldsThis eliminates redundant data storage

Three Steps of DataNormalization



214

Unnormalized Relationship

Normalized Relations (1NF)

Second Normal Form

Relations (2NF)

Third Normal Form Relations (3NF)

User View

Remove repeating groups

Remove partial dependencies

Remove transitive dependencies

Data Model Diagrams



215

Data model diagrams are used to showrelationships between attributes

An oval represents an attribute

A single arrow line represents one

A double arrow line represents many

CustomerNumber

SalespersonNumber

First Normal Form (1NF)



216

Remove any repeating groups

All repeating groups are moved into anew table

Foreign keys are used to link the tables

When a relation contains no repeating

groups, it is in the 1 NFKeys must be included to link the

relations, tables

Second Normal Form (2NF)



217

Remove any partial dependencies

A partial dependency is when the data areonly dependent on a part of a key field

A relation is created for the data thatare only dependent on part of the keyand another for data that are

dependent on both parts

Third Normal Form (3NF)



218

Remove any transitive dependencies

A transitive dependency is when a relationcontains data that are not part of the entity

The problem with transitivedependencies is updating the data

A single data item may be present on

many records

Guidelines for Creating MasterFiles or Database Relations



219

Guidelines for creating master files ordatabase relations are

Each separate entity should have it's own

master file or database relation

A specific, nonkey data field should existon only one master file or relation

Each master file or relation should haveprograms to create, read, update, anddelete records

Integrity Constraints



220

There are three integrity constraintsthat help to ensure that the databasecontains accurate data:

Entity integrity constraints, which governthe composition of primary keys

Referential integrity, which governs the

denature of records in a one-to-manyrelationship

Domain integrity



Referential Integrity



222

Referential integrity governs thedenature of records in a one-to-manyrelationship

Referential integrity means that allforeign keys in one table (the childtable) must have a matching record in

the parent table




223

Referential integrity includes

You cannot add a record without amatching foreign key record

You cannot change a primary key that hasmatching child table records

A child table that has a foreign key for adifferent record

You cannot delete a record that has childrecords




224

A restricted database updates ordeletes a key only if there are nomatching child records

A cascaded database will delete orupdate all child records when a parentrecord is deleted or changed

The parent triggers the changes

Domain Integrity



225

Domain integrity defines rules thatensure that only valid data are storedon database records

Domain integrity has two forms:

Check constraints, which are defined at thetable level

Rules, which are defined as separate objectsand may be used within a number of fields

Retrieving and PresentingDatabase Data



226

Guidelines to retrieve and present data

Choose a relation from the database

Join two relations together

Project columns from the relation

Select rows from the relation

Derive new attributes

Index or sort rowsCalculate totals and performance measures

Present data

Thank you...

Systems Analysis and Design by Keval

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