System Analysis and Design slides by Belew yenealem DTU Ethiopia

transcript

System Analysis and Design (SAD)

ByYared(Belew) YenealemDebre Tabor University,

Ethiopia

About meName: Belew Yenealem (aka. Yared)Graduated from Addis Ababa Institute

of Technology in Software Engineering.Currently an instructor at Debre Tabor

University, Computer Science Department, Ethiopia

Address: belewyenealem@gmail.com

Complete Notes and Slides for System Analysis and Design

Enjoy it!

Required Text Book

Shelly and Rosenblatt System Analysis and Design. 3rd and 8th edition

Satyinger Jacson Burd. System analysis ad Design in Changing the world. 5th editioin

William Amadio System Development a Practical Approach

Course ObjectiveUnderstand the design and development

of Computer Based Information System (CBIS) in an organization.

Know about the various aspects and components of System Life Cycle in a CBIS.

Apply the general concept of System Analysis.

Chapter 1: System-OverviewData, information, knowledge,

wisdom? What is a System?What is Analysis?What is Design?What is System Analysis?What is System Design?What is SAD?

Data vs. InformationData, information, knowledge,

wisdom? – Data- unorganized/unprocessed/ raw

facts [names, numbers, words, symbols, signs]

– Information- processed and contextualized data, meaningful [answers the questions: what, who, when, where]

Data vs. InformationData, information, knowledge,

wisdom? – Knowledge- an understanding gained

thru experience. [answers the question: How

– Wisdom- Applied knowledgeFact!=data!=information!

=knowledge!=wisdom!=future

What is a System?A collection of parts that work together to

achieve a goal/task– Examples

• Solar system• Digestive systems• Public transport system• Central heating system• Computer system• Information system

an interrelated set of business procedures (or components) used within one business unit, working together for some purpose.

Cont?Elements of System

– Input, Process, and OutputCharacteristics of a system

– Components, Interrelated components, Boundary, Purpose, env’t, interfaces, constraints, input ,and output

System concepts– Decomposition, Modularity, coupling,

and Cohesion

System Elements

INPUT OUTPUTPROCESS

FEEDBACK

System Characteristics

Characteristics of System

Components— Subsystem –an irreducible or aggregate parts in a system.

Interrelated components- dependence of one part of the system to the other [components are interrelated]

Boundary- the limits of a system, separating it from other systems.

Purpose – the overall goal/ function of the system

Environment— A system exists within an environment—everything outside the system’s boundary that influences the system

Interfaces--Point of contact where a system meets its environment or where subsystems meet each other

Constraint– a limit to what a system can accomplish

Input – System takes input from its environment

Output - System returns output to its environment as a result of its functioning to achieve the purpose. Output from individual subsystems may be inputs to other subsystems.

System conceptsDecomposition [ Why?]

– Process of breaking down a system into smaller components (parts)

Modularity– Dividing a system up into chunks or

modules of a relatively uniform size.

System concepts– .

System conceptsCoupling

– System being dependent on other systems, represents the degree to which a single unit is independent from others.

Cohesion– Extent to which a subsystem performs a single

function, represents the degree to which a part of a system forms a logically single, atomic unit.

Approach to system development

There are three strategies of IS development

1. Process-oriented approach2. Data-oriented approach3. Object-oriented approach

Process-oriented approach• An strategy to IS development that focuses on how and

when data are moved through and changed by an IS [ focuses on Process]

Data-oriented approach• An strategy to IS development that focuses on the ideal

organization of data rather than where and how data are used. [ focuses on Data]

Object-oriented approach • A system development methodologies and techniques

base on objects rather than data or process [ focuses on Object]

Information System?IS

– An arrangement of information for the purpose of supporting and improving data processing [ day to day operations in a business] and information services [problem solving and decision making]

What is an Information Systems?

Interrelated components working together to – Collect– Process– Store– Disseminate informationTo support decision making,

coordination, control, analysis and visualization in an organization

IS componentsHardware, Software, Documentation

and training materials, specific job roles, controls, and people.

IS Types

1. Transaction Processing Systems (TPS)2. Management Information Systems (MIS)3. Decision Support Systems (DSS)4. Expert System and Artificial Intelligence

(ES &AI)

Transaction Processing Systems (TPS)

TPS are computerized information systems that were developed to process large amounts of data for routine business transaction.

Automate the handling of data about business activities and transactions, which can be thought of a simple discrete events in the life of an organization.

Management Information Systems (MIS)

Information system at the management level of an organization that serves the functions of:

– planning, controlling, and decision making by providing routine summary and exception reports.

It takes the relatively raw data available through a TPS and converts them into a meaningful aggregated form that mangers need to conduct their responsibilities.

Developing an MIS calls for a good understanding of what kind of information managers require and how managers use information in their jobs.

Decision Support systems(DSS)

DSS are designed to help organizational decision make decision.

A DSS is composed of a:– Database ( may be extracted from a TPS/MIS) – Graphical/mathematical models for business

process– User interface that provides a way to

communicate with DSS

Expert System and Artificial Intelligence (ES & AI)

A system that emulates the decision-making ability of a human expert.

Designed to solve complex problems by reasoning about knowledge, like an expert.

Why SAD?

To improve organizational systems through developing or acquiring application software that can help employees accomplish key business tasks more easily and efficiently.

To create and maintain information systems that perform basic business functions.

Individual Assignment(5%)

Describe your university or college as a system. – What is the input?– What is output?– What is the boundary?– What is the components and their

relationship?– The constraint– The environment

Draw a diagram of this system

Chapter 2:

IS development Project

Managing IS ProjectProject

– a planned undertaking of a series of related activities to reach an objective that has a beginning and an end.

– a temporary attempt or endeavour made to produce some kind of a tangible or intangible result ( a unique product, service, benefit, competitive advantage, etc. )

Project ManagementThe science (theory) of:

– organizing all the project components,– stepping thru all the implementation

stages and phases,– providing and managing all the resources,– protecting the project from potential risks,– solving problems and managing changes

for the purpose of achieving initial project goals,

– developing the product, and– delivering project results

Focus of PMTo ensure that system development

projects meet customer expectations and are delivered within budget and time constraints.

Project ManagerA systems analyst with a diverse set

of skills—management, leadership, technical, conflict management, and customer relationship—who is responsible for initiating, planning, executing, and closing down a project.

Cont.Project Manager

– Systems Analyst responsible for:• Project initiation• Planning• Execution• Closing down

Project ManagerActivities

• Management• Leadership• Technical• Problem solving• Conflict management• Customer relations• Team management• Risk and change management

PMgmt. phasesInitiationPlanningExecutionClosing down

4 phases

Project PhasesPlanning (Why build the system?)Analysis (Who, what when, where

will the system be?)Design (How will the system

work?)Implementation (System delivery)

InitiationAssess the size, scope, and

complexity of the project and to establish procedures to support later project activities.

Planningfocuses on defining clear, discrete

activities and the work needed to complete each activity within a single project

Planning--WBSDividing the project into manageable

tasksGantt chart

– A graphical representation of a project that shows each task as a horizontal bar whose length is proportional to its time for completion.

Planning - COCOMOCOCOMO

– A method for estimating a software project’s size and cost.

• To estimate project resources

Planning—Network DiagramA diagram that depicts project tasks

and their interrelationships

ExecutionPrior phases are put into actionIt consists to put the planned

baseline project into action

Closingfocuses on bringing a project to an

endProjects can conclude with a natural

or unnatural termination.

Closing ActivitiesTermination

– Documentation– Personnel Appraisal

Conduct post-project reviews– Determine strengths and weaknesses of:

• Project deliverables• Project management process• Development process

Close customer contract

Techniques for Representing and Scheduling Project PlansGantt and PERT

Gantt and PERT– Gantt chart is a graphical

representation of a project that shows each task activity as a horizontal bar who is proportional to its time for completion.

– PERT chart is a diagram that represents project activities & their dependencies

• There are several tools to support Gantt and PERT charts

PERTa critical path scheduling

technique used for controlling resources and timing– PERT = Program Evaluation Review

Technique– It allows to determines critical path

scheduling and Slack Time

Gantt vs. PERTGantt

– Visually shows duration of tasks– Visually shows time overlap between tasks– Visually shows slack time

PERT– Visually shows dependencies between tasks– Visually shows which tasks can be done in

parallel– Shows slack time by data in rectangles

Gantt Chart Example

Gantt Vs. PERT

Question

Can a project have two critical paths? Why or why not? Give a brief example to illustrate your point.

Gantt, CPM, PERT

Chapter Three:System Development Life Cycle

SDLCTraditional methodology used to

develop, maintain, and replace information systems.

The SDLC is a phased approach to analysis and design that holds that systems are best developed through the use of a specific cycle of analyst and user activities.

7 phases of SDLC

4 phases of SDLCSystem Planning and SelectionSystem AnalysisSystem DesignSystem Implementation

SDLC phases

Why SDLC?SDLC has three primary objectives:

– ensure that high quality systems are delivered,

– provide strong management controls over the projects, and

– maximize the productivity of the systems staff.

Chapter 4:Systems Planning & Selectionan organization’s total information

system needs are identified, analyzed, prioritized, and arranged.

The process of – identifying, – selecting, – initiating, – planning projects and – assessing projects feasibility.

Project Identification and SelectionIdentify the need for a system

– Problems in existing system or process– New feature required in an existing

system– A new idea for which in Information

System is required– A requirement to improve efficiency in the

organization– The need to keep up with competitors

Key Sources for IS projectsManagers and business unitsIS managersFormal planning groups

Cont.Activities

– Identifying potential development projects,

– classifying and ranking projects and – selecting projects for development

Evaluation CriteriaPossible Evaluation Criteria when

classifying and ranking projects– Value chain analysis= Extent to which activities

add value and costs when developing products and/or services; information systems projects providing the greatest overall benefits will be given priority over those with fewer benefits

– Strategic alignment== Extent to which the project is viewed as helping the organization achieve its strategic objectives and long-term goals

Evaluation Criteria cont.Possible Evaluation Criteria when

classifying and ranking projects– Potential benefits== Extent to which the project

is viewed as improving profits, customer service, etc., and the duration of these benefits

– Resource availability== Amount and type of resources the project requires and their availability

Evaluation Criteria cont.Possible Evaluation Criteria when

classifying and ranking projects– Project size/duration==Number of individuals

and the length of time needed to complete the project

– Technical difficulty/risks ==Level of technical difficulty to complete the project successfully within given time and resource constraints

SelectionFactors to be considered:

– Perceived and Real needs of the organization

– Existing systems and ongoing projects– Resource availability– Evaluation criteria– Current business conditions– Perspective of the decision makers

Decision OutcomeFrom Identification and Selection:

– Accept, Reject, Delay Project – Refocus Project – End-User Development – Purchase System – Modify and Resubmit

Project Initiation and PlanningTransform a vague system

requirements into a tangible project description

The two processesInitiation

– Assess the size, scope, and complexity of the project and to establish procedures to support later project activities.

– Projects are selected, authorized, and chartered

Planning– focuses on defining clear, discrete tasks and the

work needed to complete each task

Outcome of PlanningBPP

– an internal document that contains all information collected and analyzed during initiation and planning

– reflects the best estimate of the project’s scope, benefits, costs, risks and resource requirements

SOW– a short document prepared for the customers that

describes what the project will deliver and outlines all work required to complete the project

– a useful communication tool that assures that both system analysts and customers have a common understanding of the project.

What goes into a BPP?IntroductionSystem DescriptionFeasibility AssessmentManagement Issues

What goes into a SOW?Scope of the workLocation of the workPeriod of performanceDeliverables ScheduleApplicable standardsAcceptance CriteriaSpecialized Requirements

Feasibility studyan assessment of the practicality of

a proposed plan or method.an analysis of the viability of an idea.an analysis of how successfully a

project can be completed [achievability]

Answer for :“should we proceed with the proposed project idea?

Technical feasibilityTo determine whether the company

has the technical expertise ( the organization’s ability and experience) to handle completion of the project.– Transportation– Business location– Technology needed and experience

using it– Materials and labor

Economic feasibilityInvolves a cost/ benefits analysis.determine the positive economic

benefits to the organization that the proposed system will provide.

Worthwhilenessa measure of the cost-effectiveness

of a project or solutionProvides an economic justification for

the system using cost-benefit analysis.

Legal feasibilityIn accordance to lawsComply [conform to ] with legal

requirements

Operational feasibilitya measure of how well a proposed

system – solves the problems, and – takes advantage of the opportunities

identified during scope definition and – how it satisfies the requirements

identified in the requirements analysis phase of system development

Scheduling feasibilitya measure of how reasonable the

project timetable is.Given our technical expertise, are the

project deadlines reasonable?Timetable and Deadline [cutoff date

] reasonabilitya measure of how reasonable the

project timetable is.

Political Feasibility Evaluating how KEY stakeholders

within the organization VIEW the proposed system

Chapter 5

System Analysis

Systems Analysissystem requirements are studied

and structured.The process of understanding in detail

what a system should accomplish.is the study of a business problem for

the purpose of – specifying the business requirements

for the solution and– recommending improvements

Analysisanswers the questions of:

– who will use the system, – what the system will do, and – where and when it will be used

Goal of Analysis phase– Truly understand the requirements of

a system

Analysis phase Input:

– Accepted project with baseline project plan and Work of statement

Output: – System requirement & best alternatives to design the

system• Output of phase 3 = Input of phase 4

Purpose: – How to determine requirements for the potential system? – How to structure the generated requirement? – How to select the best alternative design strategy?

Process:– Requirement determination – Requirement structuring

System AnalysisDetermine system requirementsSelect appropriate methods to elicit

system requirements from users of system– Interviews, focus groups, surveys,

discussions, or other techniques

Analysis cont.Analysis

– Study of current procedures and information systems

• Determine requirements– Study current system– Structure requirements and eliminate

redundancies• Generate alternative designs• Compare alternatives• Recommend best alternative

3 parts of AnalysisDetermining RequirementsStructuring RequirementsSelecting best alternative strategy

Req’t Determinationmore detailed, precise list of what the

new system must do to provide the needed value to the business

Answer the question: What is the system to do?

gathering information on what the system should do from as many sources as possible.

What is Req’t?a statement of what the system must

do or what characteristics it needs to have

is a characteristic or feature that must be included in an information system to be acceptable to users.

Serves as benchmarks to measure the overall acceptability of the finished system.

Req’ts Determinationgathering information on what the

system should do

Determining system Req’t Methods Traditional methods :

– Interviews– Survey via questionnaires– Direct observation of working people – Study business documents

Traditional methods of Req't gathering: Interviews

planned meeting during which you obtain information from another person

InterviewAn interview is a planned meeting

during which you obtain information from another person.

Interviewing involves getting people to recall and convey information they have.

Interview GuidelinesPlan the Interview

– Prepare interviewee by making an appointment and explaining the purpose of the interview. Prepare a checklist, an agenda, and questions.

Cont.Be Neutral

– Avoid asking leading questions [that suggest or favor a particular reply]

– For example, rather than asking, • “What advantages do you see in the

proposed system?” you might ask, • “Do you see any advantages in the proposed

system?”

Cont.Listen and take notes

– Give your undivided attention to the interviewee and take notes or tape-record the interview (if permission is granted).

Cont.Review NotesSeek diverse views

– Interview a wide range of people, including potential users and managers.

Open Ended QuestionsHave no prespecified answers.allow the respondent open options for

respondingleave room for elaboration on the part

of the interviewee.

Closed-ended questionsprovide a range of answers from which

the interviewee may choose.Limit the respondent’s options.Require a specific answerDifferent question forms

– True or False– Multiple choice– Rating a response– Ranking in some order

Probes (Probing questions)==Follow Upto go beyond the initial answer to get

more meaning, to clarify, and to draw out and expand on the interviewee’s point

Probes allow the systems analyst to follow up on questions to get more detailed responses.

Questionnaires[ኩዌሽኔር]A questionnaire, also called a survey, is a

document containing a number of standard questions that can be sent to many individuals.

is a set of written questions [either on paper or electronic] for obtaining information from individuals.

a list of questions that several people are asked so that information can be collected about something

Types of questionnaire questionsFree-format

– Open ended questionsFixed format

– Require specific responses• Multiple questions• Rating questions/ scaling• Ranking questions

L Choosing Questionnaire Respondents / RecipientsSelect a sample

– Those people who’re willing and motivated to respond

A random group– A random selection

A purposeful sample– Based on some criteria

rules for designing a good questionnaire:Allow ample white space.Allow ample space to write or type in

responses.Make it easy for respondents to clearly

mark their answers.Be consistent in style.Avoid:

– Bias, crowded pages, leading questions, threatening, abbreviations

Interviewing vs QuestionnaireInterview is more familiar and

personal than a questionnaire.During a face-to-face interview, you

can react immediately to anything the interviewee says but Questionnaire is passive.

Interviewing, however, is a costly and time-consuming process.

You seek input form a large group? Use Questionnaire!

Cont.In contrast, a questionnaire gives

many people the opportunity to provide input and suggestions

If a question, in a questionnaire, is misinterpreted, you cannot clarify the meaning as you can in a face-to-face interview.

Cont.Interview is quite time intensive and

expensive, but gives rich and detailed info, easy reaction, more familiar and personal, good for blinds.

Questionnaire– Inexpensive, take less time, good for

specific info, gathered info is less rich, passive, easy for many access, difficult for clarification if misinterpretation occurs, good for deafs.

Direct ObservationObservation, the act of watching

processes being performed, is a powerful tool to gain insight into the as-is system

gather information by watching the users of the system at work

WaysDirect Participation

– Work togetherBy watching

– Personal Observation or at a distant by camera

Analyzing DocumentsReview of existing business

documents.Useful to understand the as-is

system.

What to find in Documents?Problems with existing systems (e.g.,

missing information or redundant steps) Opportunities to meet new needs if

only certain information or information processing were available

Values and missions of the org.Influential stakeholders.Principles and rules in the org.

Types of DocumentsProcedures

– How a particular job or task is performedBusiness Forms

– What data flows in and out of the systemReports

– Primary output of current system– How data is manipulated, transformed

Manuals– Description of current IS, how to of an

existing system

Contemporary Methods– Joint Application Design – Rapid Application Design – Participatory Design– CASE tools – Prototyping

They can be used for Req’t gathering and for system development model

Why Modern?Reduces time

– Of collecting and structuring Req'tEasy and consistent data Efficiency

PrototypingDesigning and Building a scaled-down

version of the desired information system.

A prototype is an early working version of an information system.

A small-scale, incomplete, but working sample of a desired system.

a rudimentary version of an IS based on user feedback.

L PrototypingA compressed version of SDLCResembles a condensed version of

the entire SDLC

The Prototyping Method

L Prototyping

Advantages of PrototypingReduce time and costs

– the early determination of what the user really wants can result in faster and less expensive software

– the potential for changing the system early in its development,

– the opportunity to stop development on a system that is not working,

Captures Req’t in concrete forms

Contd.Improved and increased user

involvement [It involves the user in analysis and design]– prevents many misunderstandings and

miscommunications– Better feedback and specifications– User’s satisfaction – are useful in seeking user reactions,

suggestions, innovations, and revision plans

– Users can easily visualize the system from the very beginning

Disadvantages of PrototypingInsufficient AnalysisUser confusion of prototype with final

versionExcessive development time of

PrototypeDeveloper attachment to prototypeTendency to avoid formal

documentation

Process of PrototypingIdentify basic requirements

– Determine basic requirements including the input and output information desired

Contd.Develop initial prototype

– The initial prototype is developed that includes only user interfaces

Contd.Review

– The customers, including end-users, examine the prototype and provide feedback on additions or changes.

Contd.Revise and enhance the prototype

– Using the feedback both the specifications and the prototype can be improved. Negotiation about what is within the scope of the contract/product may be necessary. If changes are introduced then a repeat of steps #3 and #4 may be needed.

When to use it?User requests aren’t clearFew users are involved in the system

– Couse few won’t give detailed Req't Designs are complex and require

concrete formThere was communication problems

between analysts and usersTools are readily available to build

prototype

L Reading AssignmentDimensions of Prototyping

Horizontal and Vertical

Types of Prototyping– Throwaway– Evolutionary– Incremental– Extreme

CASE ToolsComputer-Aided/Assisted

Software/System Engineering===refers to automated software tools used by systems analysts to develop IS.

Software tools that provide automated support for some portion of the systems development process.

L Types of CASE toolsdepending on where in the

development process they are most involved in:– Upper—support analysis and design

phases– Lower—support coding phases

[Implementation]– Integrated—all phases.

ExamplesVisible Analyst WorkbenchOracle DesignerRational RoseLogic Works suite.Microsoft Visio

L Benefits : CASE ToolsTasks are much faster to complete and

alterDevelopment information is centralizedInformation is illustrated through

diagrams, which typically are easier to understand

Reduce maintenance costs, improve software quality, and enforce discipline

To assess the magnitude of changes to the project.

JAD-Joint Application DesignA structured process in which users,

managers, and analysts work together [hence Joint] for several days in a series of intensive meetings to specify or review system requirements.

A means to bring together the key users, managers, and systems analysts involved in the analysis of a current system.

Purpose: Why JAD?To collect systems requirements from

the key people involved with the system.

Allows analysts to see the areas of agreement and the areas of conflict.

To have Shared UnderstandingWhen users participate in the systems

development process, they are more likely to feel a sense of ownership in the results, and support for the new system.

L JADIn this approach, the sponsor company

creates a task force of users, managers, and IS professionals that works together to gather information, discuss business needs, and define the new system requirements. This group usually meets over periods of days or weeks.

typical JAD participantsJAD Session Leader

– Plans and leads JAD sessions– Organizes and runs the JAD– Sets the agenda and sees that it’s met– Remains neutral on issues & doesn’t

contribute ideas or opinions– Concentrate on keeping the group on

agenda, resolving conflicts and disagreements, and soliciting all ideas

Cont.Users

– Key users of the system

Cont.Managers[Project Leader]SponsorsSystem AnalystsScribe[Documentation Expert]

– The person who makes detailed notes of the happenings at a JAD session.

IS Staff– Programmers, database analysts, IS

planners, data-center personnel, developers

RAD-Rapid Application DevelopmentWhy Prototyping, CASE, JAD?

– -To facilitate development– To support RAD

To radically decrease the time needed to design and implement information systems.

Involves: extensive user involvement, prototyping, JAD sessions, integrated CASE tools, and code generators.

RAD EmphasisThe emphasis in RAD is generally less on

the sequence and structure of processes in the life cycle and more on doing different tasks in parallel with each other and on using prototyping extensively.

The main objective of all RAD approaches is to cut development time and expense by involving users in every phase of systems development.

WHEN TO USE RADConsider using RAD when:

– 1. Your team includes programmers and analysts who are experienced with it; and

– 2. There are pressing business reasons for speeding up a portion of an application development; or

– 3. When you are working with a novel ecommerce application and your development team believes that the business can sufficiently benefit over their competitors from being an innovator if this application is among the first to appear on the Web; or

– 4. When users are sophisticated and highly engaged with the organizational goals of the company

Disadvantages of RADMay try and hurry the project too

muchLoosely documentedMay not address pressing business

problemsPotentially steep learning curve for

programmers inexperienced with RAD tools

Cont.The accelerated time cycle might

allow less time to develop quality, consistency, and design standards.

PD-Participatory DesignOriginally Co-operative design, now

often co-design– is an approach to design attempting to

actively involve all stakeholders (e.g. employees, partners, customers, citizens, end users) in the design process to help ensure the result meets their needs and is usable.

L JAD vs PDThey are two established user

involvement methodologies.JAD is a practitioner-derived

methodology focusing on structured, facilitated meetings through which user involvement is elicited in systems development. PD stresses the social context of the workplace in workshops in which designers and workers collaborate in design and development activities.

Cont.Pont of Comparison JAD PDCriteria for Validation Quantitative:

economic optima, time savings, performance indices

Qualitative: democracy, mutual learning, mutual education, conflict resolution

Goal Improved System Improved Workplace

BPRThe Search for, and implementation

of, radical change in business processes to achieve breakthrough improvements in products and services.

a process in which existing methods of doing business are replaced with new and updated methods

Cont.The overall process by which current

methods are replaced with radically new methods is referred to as business process reengineering (BPR).

Deliverables and OutcomesDeliverables for Req’t determination

– From interviews and observations• Interview transcripts, observation notes,

meeting minutes– From existing written documents

• Mission and strategy statements, business forms, procedure manuals, job descriptions, training manuals, system documentation, flowcharts

– Form Computerized sources• JAD session results, CASE repositories,

reports from existing systems, displays and reports from system prototype

Structuring Req’tOrganizing a gathered Req't into a form

that is a meaningful representation of the existing system.

Structuring taking the system requirements you find during requirements determination and ordering them into tables, diagrams, and other formats that make them easier to translate into technical system specifications.

Two StagesProcess Modeling

– graphically representing the processes– Use DFD—shows mov’t of data– Logic Modeling==shows internal structure

and functionalities of the processes in DFDConceptual Data Modeling

– Shows data in a system– ER diagram—show how data is organized

in a system.

DFDShows how data moves thru an IS

but doesn’t show program logic or processing steps.

Select Best design StrategyTwo basic steps

– 1. generating a comprehensive set of alternative design strategies

– 2. Selecting the one that is most likely to result in the desired information system, given all of the organizational, economic, and technical constraints that limit what can be done.

Who’s System AnalystThe organizational role most

responsible for the analysis and design of ISs

the person in the organization most involved with systems analysis and design

Characteristics of a good SAin Req’t Determination

Chapter 6:Systems Designa description of the recommended

solution is converted into logical and then physical system specifications.

Process of defining the architecture, components, modules, interfaces, and data for a system to satisfy specified requirements.

The design phase of the SDLC uses the requirements that were gathered during analysis to create a blueprint for the future system.

System Designthe determination of the overall

system architecture—– consisting of a set of physical processing

components, hardware, software, people, and the communication among them—that will satisfy the system’s essential requirements.

DesignPhysical designArchitectural designInterface designDatabase and file designProgram designI/O Design

Activities in Design PhaseAfter detailed analysis, Determine

preferred system acquisition strategy(make, buy, or outsource)

Design the architecture for the system [Architecture Design]

Make hardware and software selections [Hardware and software specification]

Design system navigation, inputs and outputs [Interface design]

Input DesignInput mechanisms facilitate the entry of

data into the computer system, whether highly structured data, such as order information (e.g., item numbers, quantities, costs), or unstructured information (e.g., comments).

Input design means designing the screens used to enter the information, as well as any forms on which users write or type information (e.g., time cards, expense claims).

Basic Principles in IDGoal of ID

– To capture accurate information for the system simply and easily.

The fundamental principles for input design reflect the nature of the inputs (whether batch or online) and ways to simplify their collection

Principles1. Use Online and Batch

Processing Appropriately– Two general approaches for entering

inputs into a computer system: • online processing and • batch processing.

Online (Transaction) processingeach input item (e.g., a customer order, a

purchase order) is entered into the system individually, usually at the same time as the event or transaction prompting the input.– E.g., When you borrow a book from the library, buy

an item at the store, or make an airline reservation, the computer system that supports each process uses online processing to immediately record the transaction in the appropriate database(s).

Batch Processingall the inputs collected over some

period are gathered together and entered into the system at one time in a batch.

Principles 2. Capture Data at the Source

– Perhaps the most important principle of input design is to capture the data in an electronic format at the original source or as close to the original source as possible.

Principles3. Minimize KeystrokesKeystrokes cost time and money,

Types of InputsTextNumbers

Output DesignOutputs are the reports that the

system produces, whether on the screen, on paper, or in other media, such as the Web.

Output-design ObjectivesServe the intended purposeDeliver the right quantity of outputDeliver it to the right placeProvide output on timeChoose the right method

Types of Outputs

Internal outputs stay inside the system to support the system's users and managers

External outputs leave the system to trigger actions on the part of their recipients or confirm actions to their recipients – Turnaround outputs are those which are

typically implemented as a report eventually re-enters the system as an input

Prepared by Kevin C. Dittman forSystems Analysis & Design Methods 4edby J. L. Whitten & L. D. Bentley

Principles & Guidelines for Output DesignTypes of Outputs

– There are two basic types of computer outputs, external and internal.

• External outputs leave the system to trigger actions on the part of their recipients or confirm actions to their recipients.

– Most external outputs are created as preprinted forms that are designed and duplicated by forms manufacturers for use on computer printers.

– Some external outputs are designed as turnaround documents.

• Turnaround outputs are those which are typically implemented as a form eventually reenters the system as an input.

S o u n d S t a g e E n t e r t a i n m e n t C l u bF a x 3 1 7 - 4 9 4 - 0 9 9 9

T h e f o l l o w i n g n u m b e r m u s t a p p e a r o n a l l r e l a t e d c o r r e s p o n d e n c e ,s h i p p i n g p a p e r s , a n d i n v o i c e s :P . O . N U M B E R : 7 1 2 8 1 2

T o : S h i p T o :S o u n d S t a g e E n t e r t a i n m e n t C l u b S o u n d S t a g e E n t e r t a i n m e n t C l u b2 6 2 5 D a r w i n D r i v e S h i p p i n g / R e c e i v i n g S t a t i o nI n d i a n a p o l i s , I N 4 5 2 1 3 B u i l d i n g A

2 6 3 0 D a r w i n D r i v eI n d i a n a p o l i s , I N 4 5 2 1 3

P . O . D A T E R E Q U I S I T I O N E R S H I P V I A F . O . B . P O I N T T E R M S

5 - 3 - 9 6 l d b u p s N 3 0

Q T Y D E S C R I P T I O N U N I T P R I C E T O T A L

1 0 0 0 0 P o w d e r - V H S 1 9 . 9 9 1 9 9 , 9 0 0 . 0 0

5 0 0 0 N o w a n d T h e n - V H S 1 5 . 9 5 7 9 , 7 5 0 . 0 0

2 5 0 0 P u l p F i c t i o n S o u n d t r a c k - C D 7 . 9 9 1 9 , 9 7 5 . 0 0

4 5 0 U 2 o n T o u r - T - s h i r t 3 . 4 9 1 , 5 7 0 . 5 0

S u b t o t a l 3 0 1 , 1 9 5 . 5 0

T a x 1 5 , 0 5 9 . 7 7

T o t a l 3 1 6 , 2 5 5 . 2 7

1 . P l e a s e s e n d t w o c o p i e s o f y o u r i n v o i c e .

2 . E n t e r t h i s o r d e r i n a c c o r d a n c e w i t h t h e p r i c e s , t e r m s , d e l i v e r y m e t h o d , a n ds p e c i f i c a t i o n s l i s t e d a b o v e .

3 . P l e a s e n o t i f y u s i m m e d i a t e l y i f y o u a r e u n a b l e t o s h i p a s s p e c i f i e d .

M a d g e W o r t h y 5 - 4 - 9 6A u t h o r i z e d b y D a t e

I n v o i c e N o . 3 0 1 2 3 1

N a m e C a r l i n a S m i t h D a t e 7 / 2 1 / 9 7A d d r e s s 3 0 1 9 D u r o c D r i v e O r d e r N o . 3 4 6 9 1 0C i t y L i t t l e R o c k S t a t e A R Z I P 4 2 6 5 3P h o n e 5 0 2 - 4 3 0 - 4 5 4 5 P a y m e n t A m t

D e t a c h a n d r e t u r n t o p p o r t i o n w i t h p a y m e n t

Q t y D e s c r i p t i o n U n i t P r i c e T O T A L1 S t a r W a r s - E m p i r e S t r i k e s B a c k V H S $ 1 9 . 9 9 $ 1 9 . 9 91 E r i c C l a p t o n U n p l u g g e d C D $ 1 3 . 9 9 $ 1 3 . 9 91 A l l a d i n V H S $ 1 7 . 9 5 $ 1 7 . 9 5

S u b T o t a l $ 5 1 . 9 3S h i p p i n g & H a n d l i n g $ 7 . 0 0

C a s h T a x e s $ 2 . 9 5 C h e c k C r e d i t C a r d T O T A L $ 6 1 . 8 8

N a m e C C # O f f i c e U s e O n l y

E x p i r e s

R E T U R N T O P P O R T I O N W I T H P A Y M E N T

S o u n d S t a g e E n t e r t a i n m e n t C l u b2 6 3 0 D a r w i n D r i v e - B l d g BI n d i a n a p o l i s , I N 4 5 2 1 33 1 7 - 4 9 6 - 0 9 9 8 f a x 3 1 7 - 4 9 4 - 0 9 9 9 I N V O I C E

P a y m e n t D e t a i l s

C u s t o m e r

P l e a s e r e t u r n t o p p o r t i o n i n v o i c e w i t h p a y m e n t . M a k e c h e c k s p a y a b l e t o : S o u n d S t a g e E n t e r t a i n m e n t C l u b .

Principles & Guidelines for Output Design

Types of Outputs– There are two basic types of computer

outputs, external and internal. (continued)• Internal outputs stay inside the system to

support the system's users and managers.– Internal outputs fulfill management reporting and

decision support requirements. • Management information systems typically

produce three types of reports: detailed, summary, and exception.

Principles & Guidelines for Output DesignTypes of Outputs

– Internal Outputs (continued)• Detailed Reports:

– Present information with little or no filtering or restrictions.

– Some detailed reports are historical in nature.– Detailed reports confirm and document the

successful processing of transactions and serve as an audit trail for subsequent management inquiry.

• These reports assist management planning and controlling by generating schedules and analysis.

– Other detailed reports are regulatory, that is, required by government.

SOUNDSTAGE ENTERTAINMENT CLUB

Products Ordered on 6-31-1996

PO Number Product Number Product Type Quantity In Stock Quantity On Order

112312 102774 Merchandise 273 450202653 Title 75 325393752 Title 251 125

112313 109833 Merchandise 0 200111340 Title 46 150231045 Title 225 1,500253967 Title 332 850

112314 287904 Title 0 2,000699034 Merchandise 0 300836785 Merchandise 35 175984523 Title 213 250

Types of Outputs– Internal Outputs (continued)

• Summary Reports:– Categorize information for managers who do not

want to wade through details.– The data for summary reports is typically

categorized and summarized to indicate trends and potential problems.

– The use of graphics (charts and graphs) on summary reports is also rapidly gaining acceptance because it more clearly summarizes trends at a glance.

SOUNDSTAGE ENTERTAINMENT CLUB Product Sales Summary as of 7-2-1996

Product Type Product Category Current Month’s Unit Sales Current Year Unit Sales

Merchandise Clothing 784 4,312Media Accessory 541 2,079

Total:

Title Audio 3,815 20,175Game Title 1,247 5,671Video Title 2,136 9,032

Total:

Types of Outputs– Internal Outputs (continued)

• Exception Reports:– Filter data before it is presented to the manager

as information.– Exception reports only report exceptions to

some condition or standard.

SOUNDSTAGE ENTERTAINMENT CLUB

Delinquent Member Accounts as of 7-9-1996 (90 Days Overdue)

Number Name Area Code Phone Extension Balance Due

137842 Joe Dunn 317 490-0012 111 29.43142314 Bob Fischer 501 282-7996 43.97157723 Mary Slatter 218 993-9091 56.99209438 Harold Martin 823 231-8355 33.17237121 Kevin Ditmano 655 219-0988 99.23384563 Rick Carlina 501 454-6311 11.23421134 Barb Kitts 393 789-5412 231 23.66476688 Kenny Bum 443 234-8845 123.77

Principles & Guidelines for Output DesignOutput Media and Formats

– A good systems analyst will consider all available options for implementing an output, especially output medium and output format.

• A medium is what the output information is recorded on, such as paper or video display device.

• Format is the way the information is displayed on a medium for instance, columns of numbers.

– The selection of an appropriate medium and format for an output depends on how the output will be used and when it is needed.

Types of OutputsDetailed Reports:

– Present information with little or no filtering or restrictions.

– Some detailed reports are historical in nature.– Detailed reports confirm and document the successful

processing of transactions and serve as an audit trail for subsequent management inquiry.

Exception Reports:– Filter data before it is presented to the manager as

information.– Exception reports only report exceptions to some

condition or standard.

Basic PrinciplesThe goal of the output mechanism is

to present information to users so that they can accurately understand it with the least effort.

The fundamental principles for output design reflect how the outputs are used and ways to make it simpler for users to understand them.

Principles1. Understand Report Usage

– Understand how reports are used.• Real time reports• Batch reports

2. Manage Info load3. Minimize Bias

Types of Outputs

Types of OutputsInternal

– stay inside the system to support the system's users and managers

External– Reports– Media

Output FormatsTabularZonedGraphicNarrative

Data Storage FormatsTypes

– Files• Electronic lists of data that have been

optimized to perform a particular transaction.– Database

• a collection of groupings of information that are related to each other in some way (e.g., through common fields).

Logical and Physical Design

Steps to develop Logical Database Model

Purpose of designing Logical DBTo structure the data in stable structures

Minimal redundancyTo meet actual data requirements of the

systemTo ease physical database design

Relational Database ModelAn approach to managing data

using tuplesOrganizes data in tables

Primary KeyUniquely identifies a record in a tableCannot accept null valuesA table typically has a column or combination of

columns that contain values that uniquely identify each row in the table. This column, or columns, is called the primary key (PK) of the table and enforces the entity integrity of the table. Because primary key constraints guarantee unique data, they are frequently defined on an identity column.

Foreign Keya field in the table that is primary

key in another table.

Normalizationused to produce a data model that

has the properties of – simplicity, – non-redundancy and – minimal maintenance.

Referential Integritya property of data which, when

satisfied, requires every value of one attribute (column) of a relation (table) to exist as a value of another attribute (column) in a different (or the same) relation (table)

Dependency

Group Assignments / 5%Briefly Discuss about the following

Concepts:– Logical and Physical Database– How to design a logical Database and a

physical database?– Relational database model – Primary key and foreign key – Normalization – Referential Integrity – Dependency

Chapter 7:Systems Implementation and Maintenancethe information system is coded,

tested, installed and supported in the organization.

System implementationis the construction, installation and

testing of system components and the delivery of the system for day-to-day operation.

Expensive phaseTime consuming

– So many people involved

Maintenancean information system is

systematically repaired and improved

Repairing, Looking after, improving

System Implementation & OperationInstall systemPrepare documentationTrain users of the systemProvide supportMaintain system on a regular basis

7 major activitiesCodingTestingInstallationDocumentationTrainingSupportMaintenance

1. Codingturning the physical design

specifications created at the design stage into working computer code by programmers.

Coding is the process of turning program logic into specific instructions that the computer system can execute. Working from a specific design, a programmer uses a programming language to transform program logic into code statements.

2. TestingStatic and dynamic testing

Whether code is executed or not

Automated and manual testing– Whether testing is done manually or not

7 types of tests, their category

Inspectionparticipants manually examine code

for occurrences of well-known errors. Syntax, grammar and some other routine errors can be checked by automated inspection software, so manual inspection checks are used for more subtle errors.

Exactly what the code does is not investigated in an inspection.

WalkthroughReviewing what the code does and

thereby finding out errorsCode review

Desk-checkingA testing technique in which the

program code is sequentially executed manually by the reviewer.

A manual (non-computerized) technique for checking the logic of an algorithm.

Syntax checkingDone by the computer/compilerCode not executed

Unit(module/functional)TestingEach module is tested alone in an

attempt to discover any errors in its code.

Integration TestingCombining modules and testing them

System Testingtesting of the IS as a whole (as a

complete entity)The bringing together for testing

purposes of all the programs that a system comprises.

Stub TestingA technique used in testing modules,

especially where modules are written and tested in a top-down fashion, where a few lines of code are used to substitute for subordinate modules.

Stubs are two or three lines of code written by a programmer to stand in for the missing modules

Acceptance Testing by UsersAcceptance Testing

– The process whereby actual users test a completed information system, the end result of which is the users’ acceptance of it once they are satisfied with it.

testing the system in the environment where it will eventually be used

3. InstallationCalled System conversionThe process of moving from the

current information system to the new one

The organizational process of changing over from the current information system to a new one

Installation Strategies/approachesDirect Installation [Abrupt cut-over]

– old system is terminated on a specific date and the new system is placed into operation.

– High risk approachChanging over from the old

information system to a new one by turning off the old system when the new one is turned on.

Cont.Parallel Installation

– both the old and new systems are operated for some time period

– Old and new systems coexistRunning the old information system

and the new one at the same time until management decides the old system can be turned off.

running the old system and the new system at the same time, in parallel.

Cont.Phased Installation

– Changing from the old information system to the new one incrementally, starting with one or a few functional components and then gradually extending the installation to cover the whole new system

Staged, incremental, gradual, based on system functional components

Cont.Single location installation [Pilot

Installation/Operation]– involves implementing the complete new

system at a selected location of the company.

– Trying out a new information system at one site and using the experience to decide if and how the new system should be deployed throughout the organization.

4.DocumentationDocumentation describes an

information system and helps the users, managers, and IT staff who must interact with it. Accurate documentation can reduce system downtime, cut costs, and speed up maintenance tasks

Types of DocumentationSystem Documentation

– detailed information about a system’s design specifications, its internal workings, and its functionality.

– describes the system’s functions and how they are implemented.

– is a by-product of the systems analysis and design process and is created as the project unfolds.

Types cont.User Documentationconsists of written or other visual

information about an application system, how it works and how to use it

Reference guide, user’s guide, release description, system admins guide, acceptance sign-off

5. TrainingThe educational process in which

systems analysts engage in to bring about the smooth transition from the old system to the new is called training.

Issues to considerWho to Train?

– anyone whose work is affected by the new information system

– All users [both primary and secondary]• From data entry personnel to decision makers

Who be Trainers?– Vendors – Systems analysts – External paid trainers – In-house trainers – Other system users

Issues to considerWhat to Train?

– Use of system – General computer concepts – IS concepts (batch Vs. online processing) – Organizational practice concepts ( e.g.

FIFO inventory accounting) – System management (e.g. how to

request changes to a system) – System installation

Types of Training MethodsFormal courses —several people taught

at the same timeResident expertE-learning/distance learningBlended learning (combination of

instructor-led training and e-learning)Software help componentsTutorial ---one person taught at a timeExternal sources, such as vendors

6. User Supportan ongoing technical support provided

to users Providing ongoing educational and

problem-solving assistance to information system users.

User support in an organization is usually provided in two forms: – an information center and – a help desk.

7. MaintenanceIs the process of refining the system

to make sure it continues to meet business needs.

Types of MaintenanceCorrective

– To fix errors and problems– diagnoses and corrects errors in an

operational system– repair defects in the design, coding, or

implementation of an IS.

Types of MaintenanceAdaptive

– Adds new capability and enhancements

– involves making changes to an information system to evolve its functionality to changing business needs

Types of MaintenancePerfective

– Improving efficiency, reliability, or maintainability

– involves changes made to a system to reduce the chance of future system failure.

Types of MaintenancePreventive

– reduces the possibility of future system failure.

– Avoids future problems– Detailed analysis of areas where troubles

are likely to occur.

Processes and Deliverables

Process Product

Planning

Analysis

Design

Implementation

Project Plan

System Proposal

System Specification

New System and Maintenance Plan

SDLC criticisms…Reliance on the life cycle approach

forced intangible and dynamic processes such as analysis and design into timed phases that were doomed to fail. (martin, 1999)

Massive amount of processes and documentation does slow down development, Agile developers claims that source code is enough documentation.

Cont. CriticismCriticism of the SDLC that is based on

fiction is that all versions of SDLC are waterfall-like with no feedback between steps.

Another false criticism is that a life cycle approach limits the involvement of users, yet Agile and Extreme programming approaches advocate an analysis-design-code-test sequence, and that is itself is a cycle.