system analysis and design slides by belew yenealem dtu ethiopia
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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: [email protected]
Viva!
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
Characteristics of 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
Characteristics of System
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]
1.14
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.
1.23
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 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
SDLC
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.
CDM
LDM
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.
Prepared by Kevin C. Dittman forSystems Analysis & Design Methods 4edby J. L. Whitten & L. D. Bentley
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
Prepared by Kevin C. Dittman forSystems Analysis & Design Methods 4edby J. L. Whitten & L. D. Bentley
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 .
Prepared by Kevin C. Dittman forSystems Analysis & Design Methods 4edby J. L. Whitten & L. D. Bentley
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.
Prepared by Kevin C. Dittman forSystems Analysis & Design Methods 4edby J. L. Whitten & L. D. Bentley
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.
Prepared by Kevin C. Dittman forSystems Analysis & Design Methods 4edby J. L. Whitten & L. D. Bentley
Page 1SOUNDSTAGE 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
Prepared by Kevin C. Dittman forSystems Analysis & Design Methods 4edby J. L. Whitten & L. D. Bentley
Principles & Guidelines for Output Design
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.
Prepared by Kevin C. Dittman forSystems Analysis & Design Methods 4edby J. L. Whitten & L. D. Bentley
Page 1SOUNDSTAGE 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:
Prepared by Kevin C. Dittman forSystems Analysis & Design Methods 4edby J. L. Whitten & L. D. Bentley
Principles & Guidelines for Output Design
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.
Prepared by Kevin C. Dittman forSystems Analysis & Design Methods 4edby J. L. Whitten & L. D. Bentley
Page 1SOUNDSTAGE 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
Prepared by Kevin C. Dittman forSystems Analysis & Design Methods 4edby J. L. Whitten & L. D. Bentley
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.