Phân tích hệ thống

Information Systems
Analysis and Design
Myriam Lewkowicz
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Outline
Information Systems: the big picture
Information Systems for competitive advantage
Organizational Information Systems
Entreprise-Wide Information Systems
Information Systems Development & Acquisition
Managing the Information Systems Project
Systems Planning
Determining System Requirements
Structuring System Requirements: Process Modeling
Structuring System Requirements: Conceptual Data Modeling
Object Oriented Analysis and Design
Designing the Human Interface
Systems Implementation and Operation
Chapter 1

Information Systems:
The Big Picture
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Chapter 1 Objectives
Understand the term information systems (IS)
Understand IS components:
Technology, people, organizations
Understand IS career opportunities
Understand types of information systems
Understand IS and organizational success or failure
Understand the future of IS management
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Information Systems Defined
Combinations of hardware, software, and telecommunications networks that people build and use to collect, create, and distribute useful data in organizations
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Key Elements of Information Systems
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Data
Data: raw material, unformatted information
Information: processed data (meaningful)
Knowledge: understanding relationships between pieces of information
Wisdom: knowledge accumulated and applied
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Knowledge as a Business Resource
Knowledge Worker
A well-educated professional who creates, modifies, or synthesizes knowledge in one’s profession
Knowledge Society
Also called digital society, new economy
Working with brains instead of hands
The importance of education
Digital divide
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Technology and Information Systems
Computer-Based Information Systems
One type of technology
Technology – any mechanical and/or electrical means to supplement, extend, or replace human activity
Information Technology (IT) – machine technology controlled by or using information

The goal of IS is to provide useful data to users
IS can be local or global, organizational or enterprise-wide
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IS Managerial Personnel
CIO
IS director
Account Executive
Info Center Manager
Development Manager
Project Manager
Maintenance Manager
Systems Manager
IS planning Manager
Operations Manager
Programming Manager
Systems Programming Manager
Manager of Emerging Technologies
Telecommunications Manager
Network Manager
Database Administrator
Auditing or Computer Security Manager
Quality Assurance Manager
Webmaster
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Integrating Skills and Knowledge
Technology
hardware, software, networking
Business
business, management, social, communications
Systems
Integration, development methods, critical thinking, problem solving
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Hot Skills in IS Workers
Office / E-mail
Languages
Applications
RDBS Administration
Development Tools
Internetworking
Operating Systems
LAN Administration
Networking
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IS Within the Firm
Traditionally a love/hate relationship
“Techies” vs. mere “users” (us vs. them)
Poor service, lousy attitudes
Now: progress toward better customer service
Better relationships within the company
Cooperation, not rivalry
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The Spread of Technology in Organizations
Technology infiltrates business units
Dual role for IS workers:
Work with IS technical group
Work with business unit (marketing, finance, etc.)
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The Spread of Technology in Organizations
Benefits of centralized IS function
Coordinated planning
Consistent management
Systems compatibility and connectivity
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Questions
Define and understand the term information systems (IS)
Explain the technology, people, and organizational components of an information system.

Chapter 2

Information Systems for Competitive Advantage
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Chapter 2 Objectives
Understand the IS in automation, organizational learning, and strategic support
Understand IS for strategic organizational success
Understand the need for making an IS business case
Understand technological innovations to improve competitive advantage
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Why Use Information Systems?
Automating: doing things faster
Organizational learning: doing things better
Supporting Strategy: doing things smarter
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Automating:
Doing Things Faster
Technology is used to automate a manual process
Doing things faster, better, cheaper
Greater accuracy and consistency
Loan application example
Manual processing
Technology-supported process
Completely automated
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Organizational Learning:
Doing Things Better
Going beyond automation
Involves learning to improve the day-to-day activities within the process
Looking at patterns and trends
Organizational Learning
Using acquired knowledge and insights to improve organizational behavior
Total Quality Management (TQM)
Monitoring an organization to improve quality of operations, products, and services
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Supporting Strategy:
Doing Things Smarter
Strategic Planning
Create a vision: setting the direction
Create a standard: performance targets
Create a strategy: reaching the goal
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Question
Now, it should be fairly obvious why an IS professional should be able to make a business case for a given system. Why, however, is it just as important for non-IS professionals? How are they involved in this process? What is their role in information systems planning?
Chapter 3
Organizational
Information Systems
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Chapter Objectives
Understand characteristics of operational, managerial, and executive information systems
Understand characteristics of transaction processing systems, management information systems, and executive information systems
Understand characteristics of information systems that span organizational boundaries
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Decision-Making Levels of an Organization
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Decision-Making Levels of an Organization
Executive level (top)
Long-term decisions
Unstructured decisions
Managerial level (middle)
Decisions covering weeks and months
Semistructured decisions
Operational level (bottom)
Day-to-day decisions
Structured decisions

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General Types of Information Systems
Transaction Processing Systems (TPSs)
Transactions
Used at Operational level of the organization
Goal: to automate repetitive information processing activities
Increase speed
Increase accuracy
Greater efficiency
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General Types of Information Systems
Data input
Manual data entry
Semiautomated data entry
Fully automated data entry
Examples:
Payroll
Sales and ordering
Inventory
Purchasing, receiving, shipping
Accounts payable and receivable
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General Types of Information Systems
Management Information Systems (MISs)
Two Types:
Management of IS in organizations
Specific information systems for mid-level managers
Used at managerial level of the organization
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General Types of Information Systems
Management Information Systems
Types of reports:
Scheduled report
Key-indicator report
Exception report
Drill-down report
Ad hoc report
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General Types of Information Systems
Management Information Systems (MISs)
Examples:
Sales forecasting
Financial management and forecasting
Manufacturing planning and scheduling
Inventory management and planning
Advertising and product pricing

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General Types of Information Systems
Executive Information Systems (EISs)
Used at executive level of the organization
Highly aggregated form
Data types
Soft data – news and nonanalytical data
Hard data – facts and numbers

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General Types of Information Systems
Executive Information Systems (EISs)
Examples:
Executive-level decision making
Long-range and strategic planning
Monitoring internal and external events
Crisis management
Staffing and labor relations

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Information Systems that Span Organizational Boundaries
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Information Systems that
Span Organizational Boundaries
Decision Support Systems (DSSs)
Designed to support organizational decision making
“What-if” analysis
Example of a DSS tool: Microsoft Excel
Text and graphs
Models for each of the functional areas
Accounting, finance, personnel, etc.

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Information Systems that
Span Organizational Boundaries
Expert Systems (ESs)
Mimics human expertise by manipulating knowledge
Rules (If-then)
Inferencing

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Information Systems that
Span Organizational Boundaries
Office Automation Systems (OASs)
Examples:
Communicating and scheduling
Document preparation
Analyzing data
Consolidating information
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Information Systems that
Span Organizational Boundaries
Collaboration Technologies
Virtual teams
Videoconferencing
Groupware
Electronic Meeting Systems (EMSs)
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Information Systems that
Span Organizational Boundaries
Functional Area Information Systems
Geared toward specific areas in the company:
Human Resources
Benefits
Marketing


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Information Systems that
Span Organizational Boundaries
Global Information Systems
International IS
Transnational IS
Multinational IS
Global IS


Chapter 4
Enterprise-Wide
Information Systems
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Chapter Objectives
Understand how information technology supports business activities
Understand enterprise systems and how they evolved
Understand software applications that are internally or externally focused
Understand how to implement enterprise systems
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Enterprise Systems
Enterprise systems
Also known as enterprise-wide information systems
Information systems that allow companies to integrate information across operations on a company-wide basis
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Before an entreprise system
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With an entreprise sytem
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Types of Enterprise Systems
Packaged applications
Custom applications
Stand-alone applications
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Types of Enterprise Systems
Enterprise Resource Planning
Integrated applications
ERP systems
Baan
Oracle
PeopleSoft
SAP
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Types of Enterprise Systems
ERP Implementation
Modules
Customizations
Best practices
Business process reengineering (BPR)
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Types of Enterprise Systems
Customer Relationship Management (CRM)
Sales Force Automation (SFA)
New opportunities for competitive advantage
Examples:
MGM
American Airlines
Marriott International
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CRM system
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Types of Enterprise Systems
Supply Chain Management (SCM)
Supply chain – the producers of supplies that a company uses
Supply network
What if supply chain does not collaborate?
Two objectives of upstream information flow:
Accelerate product development
Reduce costs associated with suppliers
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Supply chain management
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The Formula for Enterprise System Success
Secure executive sponsorship
Get help from outside experts
Thoroughly train users
Take a multidisciplinary approach to implementation
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Questions
List the different classes of information systems described in this chapter. How do they differ from each other?
Of the information systems listed in the chapter, how many do you have experience with? What systems would you like to work with? What types of systems do you encounter at the university you are attending?
Consider an organization that you are familiar with, perhaps the one in which you work or one with which you have done business. Describe the type of information systems that organization uses and whether or not they are useful or up-to-date. List specific examples for updating or installing information systems that improve productivity or efficiency.
Chapter 5
Information Systems
Development & Acquisition
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Chapter Objectives
Understand the process of IS management
Understand the system development life cycle (SDLC)
Understand alternative approaches to system development
Understand in-house system development
Understand external acquisition, outsourcing, and end-user development

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The Need for Structured Systems Development
Systems analysis and design – the process of designing, building, and maintaining information systems
Systems analyst
Blending technical and managerial expertise
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The Need for Structured Systems Development
Evolution of IS development
From “art” to a “discipline”
Standardized development methods
Software engineering
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The Need for Structured Systems Development
Options for Obtaining Information Systems
Build your own
Buy a prepackaged system
Outsource development to a 3rd party
End user development
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The Need for Structured Systems Development
Information Systems Development in Action
Breaking large complex problems into manageable pieces
Decomposing large, complex problems
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The Need for Structured Systems Development
System Construction Process
Identify a large IT problem to solve
Break the large problem into several smaller, more manageable pieces
Translate each “piece” (small problem) into computer programs
Piece together each program into an overall comprehensive IS that solves the problem
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The Need for Structured Systems Development
The Role of Users in the Systems Development Process
Knowledgeable of needs
Effective partnership
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Information Systems Analysis and Design
Systems Analyst performs analysis and design based upon:
Understanding of organization’s objectives, structure and processes
Knowledge of how to exploit information technology for advantage

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Systems Analysis and Design: Core Concepts
Major goal: to improve organizational systems by developing or acquiring software and training employees in its use
Application software, or a system, supports organizational functions or processes
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Systems Analysis and Design: Core Concepts
System: Turns data into information and includes:
Hardware and system software
Documentation and training materials
Job roles associated with the system
Controls to prevent theft or fraud
The people who use the software to perform their jobs
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Software Engineering Process
A process used to create an information system
Consists of:
Methodologies
A sequence of step-by-step approaches that help develop the information system
Techniques
Processes that the analyst follows to ensure thorough, complete and comprehensive analysis and design
Tools
Computer programs that aid in applying techniques
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System
A system is an interrelated set of business procedures used within one business unit working together for a purpose
A system has nine characteristics
A system exists within an environment
A boundary separates a system from its environment
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Characteristics of a System
Components
Interrelated Components
Boundary
Purpose
Environment
Interfaces
Constraints
Input
Output
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Important System Concepts
Decomposition
The process of breaking down a system into smaller components
Allows the systems analyst to:
Break a system into small, manageable subsystems
Focus on one area at a time
Concentrate on component pertinent to one group of users
Build different components at independent times
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Important System Concepts
Modularity
Process of dividing a system into modules of a relatively uniform size
Modules simplify system design
Coupling
Subsystems that are dependent upon each other are coupled
Cohesion
Extent to which a subsystem performs a single function
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A Modern Approach to Systems Analysis and Design
Systems Integration
Allows hardware and software from different vendors to work together
Enables procedural language systems to work with visual programming systems
Visual programming environment uses client/server model
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Data and Processes
Three key components of an information system
Data
Data Flows
Processing Logic
Data vs. Information
Data
Raw facts
Information
Derived from data
Organized in a manner that humans can
understand


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Data and Processes
Data
Understanding the source and use of data is key to good system design
Various techniques are used to describe data and the relationship amongst data
Data Flows
Groups of data that move and flow through the system
Include description of sources and destination for each data flow
Processing Logic
Describe steps that transform data and events that trigger the steps

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Approaches to Systems Development
Process-Oriented Approach
Focus is on flow, use and transformation of data in an information system
Involves creating graphical representations such as data flow diagrams and charts
Data are tracked from sources, through intermediate steps and to final destinations
Natural structure of data is not specified
Disadvantage: data files are tied to specific applications
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Approaches to Systems Development (2)
Data-Oriented Approach
Depicts ideal organization of data, independent of where and how data are used
Data model describes kinds of data and business relationships among the data
Business rules depict how organization captures and processes the data
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Databases and Application Independence
Database
Shared collection of logically related data
Organized to facilitate capture, storage and retrieval by multiple users
Centrally managed
Designed around subjects
Customers
Suppliers
Application Independence
Separation of data and definition of data from applications

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Role of the Systems Analyst
Study problems and needs of an organization
Determine best approach to improving organization through use of:
People
Methods
Information technology
Help system users and managers define their requirements for new or enhanced systems

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Role of the Systems Analyst
Assess options for system implementation
In-house development
Outsourced development
Outsourced development and operation
Commercial application
For in-house projects, work on a team of analysts and developers
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Skills of a Successful Systems Analyst
Analytical
Understanding of organizations
Problem-solving skills
System thinking
Ability to see organizations and information systems as systems
Technical
Understanding of potential and limitations of technology
Managerial
Ability to manage projects, resources, risk and change
Interpersonal
Effective written and oral communication skills
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Systems Development Life Cycle
System Development Methodology
Standard process followed in an organization
Consists of:
Analysis
Design
Implementation
Maintenance
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Systems Development Life Cycle
Series of steps used to manage the phases of development for an information system
Consists of four phases:
Planning and Selection
Analysis
Design
Implementation and Operation
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Systems Development Life Cycle
Phases are not necessarily sequential
Each phase has a specific outcome and deliverable
Individual companies use customized life cycle
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Phases of the Systems Development Life Cycle
Systems Planning and Selection
Two Main Activities
Identification of need
Investigation and determination of scope
Systems Analysis
Study of current procedures and information systems
Determine requirements
Generate alternative designs
Compare alternatives
Recommend best alternative
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Systems Development Life Cycle
System Design
Logical Design
Concentrates on business aspects of the system
Physical Design
Technical specifications
Implementation and Operation
Implementation
Hardware and software installation
Programming
User Training
Documentation
Operation
System changed to reflect changing conditions
System obsolescence
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Alternative approaches
Prototyping
Building a scaled-down working version of the system
Advantages:
Users are involved in design
Captures requirements in concrete form
Rapid Application Development (RAD)
Utilizes prototyping to delay producing system design until after user requirements are clear
Joint Application Design (JAD)
Users, Managers and Analysts work together for several days
System requirements are reviewed
Structured meetings
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Summary
Information systems analysis and design
Process of developing and maintaining an information system
Modern approach to systems analysis
Process-Oriented
Data-Oriented
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Summary
Systems Development Life Cycle (SDLC)
Systems Planning and Selection
Systems Analysis
Systems Design
Systems Implementation
Alternatives to Systems Development Life Cycle
Prototyping
Rapid Application Development (RAD)
Joint Application Design (JAD)
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Questions
In what way are organizations systems?
List and explain the different phases in the systems development life cycle.
Why is it important to use systems analysis and design methodologies when building a system? Why not just build the system in whatever way seems to be “quick and easy”? What value is provided by using an “engineering” approach?
Explain the traditional application-based approach to systems development. How is this different from the data-based approach?
What is prototyping?
What is JAD? What is Participatory Design?

Chapter 6
Managing the Information Systems Project
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Learning Objectives
Discuss skills required to be an effective project manager
Describe skills and activities of a project manager during project initiation, planning, execution and closedown
Explain Gantt Charts and Network Diagrams
Review commercial project management software packages
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Case of Pine Valley Furniture
Manufacturing Company
Product: Wood Furniture
Market: U.S.
Organized into functional areas
Manufacturing
Sales
Three independent computer systems were converted to a database in 1990s
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Managing the Information Systems Project
Focus of project management
To ensure that information system projects meet customer expectations
Delivered in a timely manner
Meet constraints and requirements
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Project Manager
Systems Analyst responsible for
Project initiation
Planning
Execution
Closing down
Requires diverse set of skills
Management
Leadership
Technical
Conflict management
Customer relations
Managing the Information Systems Project
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Project Management Process
Project
Planned undertaking of related activities to reach an objective that has a beginning and an end
Four Phases
Initiation
Planning
Execution
Closing down
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Initiating the Project
Establish project initiation team
Establish relationship with customer
Establish project initiation plan
Establish management procedures
Establish project management environment and workbook
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Planning the Project
Describe project scope, alternatives and feasibility
Scope and Feasibility
Understand the project
What problem is addressed
What results are to be achieved
Measures of success
Completion criteria



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Planning the Project
Divide the project into manageable tasks
Work breakdown structure
Gantt chart
Estimate resources and create a resource plan
Develop a preliminary schedule
Utilize Gantt Charts and Network Diagrams
Develop a communication plan
Outline communication processes among customers, team members and management
Types of reports
Frequency of reports
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Planning the Project
Determine project standards and procedures
Specify how deliverables are tested and produced
Identify and assess risk
Identify sources of risk
Estimate consequences of risk
Create a preliminary budget
Develop a statement of work
Describe what the project will deliver
Set a baseline project plan
Estimate of project’s tasks and resources

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Executing the Project
Execute baseline project plan
Acquire and assign resources
Train new team members
Keep project on schedule
Monitor project progress
Adjust resources, budget and/or activities
Manage changes to baseline project plan
Slipped completion dates
Changes in personnel
New activities
Maintain project workbook
Communicate project status
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Closing Down the Project
Termination
Types of termination
Natural
Requirements have been met
Unnatural
Project stopped
Documentation
Personnel Appraisal
Conduct post-project reviews
Determine strengths and weaknesses of:
Project deliverables
Project management process
Development process
Close customer contract
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Representing and Scheduling Project Plans
Gantt Charts
Useful for depicting simple projects or parts of large projects
Show start and completion dates for individual tasks
Network Diagrams
Show order of activities
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Summary
Skills of an effective project manager
Activities of project manager
Initiation
Planning
Execution
Closedown
Gantt Charts and Network Diagrams
Commercial PM Software
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Questions
List and describe the common skills and activities of a project manager. Which skill do you think is most important? Why?
Describe the activities performed by the project manager during project initiation.
Describe the activities performed by the project manager during project planning.
Describe the activities performed by the project manager during project execution.
Chapter 7
Systems Planning
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Learning Objectives
Discuss the content of and need for a Statement of Work and Baseline Project Plan
Describe a structured walkthrough
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First documents
Baseline Project Plan (BPP) : internal document
Scope
Benefits
Costs
Risks
Resources
Statement of Work (SOW) : Outlines objectives and constraints of the project to the customer
Describes deliverables
Outlines work needed to be performed
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Building the Baseline Project Plan
Objectives
Assures that customer and development group have a complete understanding of the proposed system and requirements
Provides sponsoring organization with a clear idea of scope, benefits and duration of project
Four Sections
Introduction
System Description
Feasibility Assessment
Management Issues
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Building the Baseline Project Plan
Introduction
Brief overview
Recommended course of action
Project scope defined
Units affected
Interaction with other systems
Range of system capabilities
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Building the Baseline Project Plan
System Description
Outline of possible alternative solutions
Narrative format
Feasibility Assessment
Project costs and benefits
Technical difficulties
High-level project schedule
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Building the Baseline Project Plan
Management Issues
Outlines concerns that management may have about the project
Team composition
Communication plan
Project standards and procedures
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Reviewing the Baseline Project Plan
Objectives
Assure conformity to organizational standards
All parties agree to continue with project
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Reviewing the Baseline Project Plan
Walkthrough
Peer group review
Participants
Coordinator
Presenter
User
Secretary
Standards Bearer
Maintenance Oracle
Activities
Walkthrough review form
Individuals polled
Walkthrough action list
Advantages
Assures that review occurs during project
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Summary
Baseline Project Plan (BPP)
Created during project initiation and planning
Contains:
Introduction
High-Level description of system
Outline of feasibility
Overview of Management Issues
Statement of Work (SOW)
Describes what project will deliver
Lists all work to be performed

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Questions
What is contained in a Baseline Project Plan? Are the content and format of all baseline plans the same? Why or why not?
Describe the structured walkthrough process. What roles need to be performed during a walkthrough?

Chapter 8
Determining System Requirements
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Learning Objectives
Describe options for designing and conducting interviews
Discuss planning an interview
Discuss using questionnaires to determine system requirements
Explain advantages and disadvantages of observing workers and analyzing business documents to determine requirements
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Learning Objectives
Learn about Joint Application Design (JAD) and Prototyping
Discuss appropriate methods to elicit system requests
Examine requirements determination for Internet applications
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Activities in Requirement Gathering
1.0
Identify the right
Stakeholders &
Artefacts
0.0
Outline information
to be sought
2.0
Use most appropriate
investigation techniques
4.0
Document the
requirements
Objective: determine the functions & information that must be provided by the information system
3.0
Determine duration
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Performing Requirements Determination
Gather information on what the system should do from many sources
Users
Reports
Forms
Procedures
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Performing Requirements Determination
Characteristics for gathering requirements
Impertinence
Question everything
Impartiality
Find the best organizational solution
Relaxation of constraints
Attention to detail
Reframing
View the organization in new ways
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Deliverables and Outcomes
Types of deliverables:
Information collected from users
Existing documents and files
Computer-based information
Understanding of organizational components
Business objective
Information needs
Rules of data processing
Key events
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Deliverables and Outcomes
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Traditional Methods for Determining Requirements
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Traditional Methods for Determining Requirements
Interviewing and Listening
Gather facts, opinions and speculations
Observe body language and emotions
Guidelines
Plan
Checklist
Appointment
Be neutral
Listen
Seek a diverse view
Interview Questions
Open-Ended
No prespecified answers
Close-Ended
Respondent is asked to choose from a set of specified responses
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Traditional Methods for Determining Requirements
Administering Questionnaires
More cost-effective than interviews
Choosing respondents
Should be representative of all users
Types of samples
Convenient
Random sample
Purposeful sample
Stratified sample
Design
Mostly closed-ended questions
Can be administered over the phone, in person or over the Internet or company intranet
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Traditional Methods for Determining Requirements
Questionnaires Vs. Interviews
Interviews cost more but yield more information
Questionnaires are more cost-effective
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Traditional Methods for Determining Requirements
Directly Observing Users
Serves as a good method to supplement interviews
Often difficult to obtain unbiased data
People often work differently when being observed
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Analyzing Procedures and Other Documents
Types of information to be discovered:
Problems with existing system
Opportunity to meet new need
Organizational direction
Names of key individuals
Values of organization
Special information processing circumstances
Rules for processing data
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Modern Methods for Determining Requirements
Joint Application Design (JAD)
Brings together key users, managers and systems analysts
Purpose: collect system requirements simultaneously from key people
Conducted off-site
Prototyping
Repetitive process
Rudimentary version of system is built
Replaces or augments SDLC
Goal: to develop concrete specifications for ultimate system
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Joint Application Design (JAD)
Participants
Session Leader
Users
Managers
Sponsor
Systems Analysts
Scribe
IS Staff
End Result
Documentation detailing existing system
Features of proposed system
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Prototyping
Quickly converts requirements to working version of system
Once the user sees requirements converted to system, will ask for modifications or will generate additional requests
Most useful when:
User requests are not clear
Few users are involved in the system
Designs are complex and require concrete form
History of communication problems between analysts and users
Tools are readily available to build prototype
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Prototyping
Drawbacks
Tendency to avoid formal documentation
Difficult to adapt to more general user audience
Sharing data with other systems is often not considered
Systems Development Life Cycle (SDLC) checks are often bypassed
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Summary
Interviews
Open-ended and close-ended questions
Preparation is key
Questionnaires
Must be carefully designed
Can contain close-ended as well as open-ended questions
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Summary
Other means of gathering requirements
Observing workers
Analyzing business documents
Joint Application Design (JAD)
Prototyping
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Questions (1)
Describe systems analysis and the major activities that occur during this phase of the systems development life cycle.
What are some useful character traits for an analyst involved in requirements determination?
Describe four traditional techniques for collecting information during analysis. When might one be better than another?
What are the general guidelines for conducting interviews?
What are the general guidelines for designing questionnaires?
Compare collecting information by interview and by questionnaire. Describe a hypothetical situation in which each of these methods would be an effective way to collect information system requirements.
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Questions (2)
What are the general guidelines for collecting data through observing workers?
What are the general guidelines for collecting data through analyzing documents?
Describe how prototyping can be used during requirements determination. How is it better or worse than traditional methods?
Chapter 9
Structuring System Requirements:
Process Modeling

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Learning Objectives
Understand the logical modeling of processes through studying data flow diagrams
How to draw data flow diagrams using rules and guidelines
How to decompose data flow diagrams into lower-level diagrams
Balancing of data flow diagrams
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Learning Objectives
Discuss the use of data flow diagrams as analysis tools
Discuss process modeling for Internet Applications
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Process Modeling
Graphically represent the processes that capture, manipulate, store and distribute data between a system and its environment and among system components
Data flow diagrams (DFD)
Graphically illustrate movement of data between external entities and the processes and data stores within a system
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Process Modeling
Modeling a system’s process
Utilize information gathered during requirements determination
Structure of the data is also modeled in addition to the processes
Deliverables and Outcomes
Set of coherent, interrelated data flow diagrams
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Process Modeling
Deliverables and outcomes (continued)
Context data flow diagram (DFD)
Scope of system
DFDs of current system
Enables analysts to understand current system
DFDs of new logical system
Technology independent
Show data flows, structure and functional requirements of new system
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Data Flow Diagramming Mechanics
Data Flow
Depicts data that are in motion and moving as a unit from one place to another in the system
Drawn as an arrow
Select a meaningful name to represent the data
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Data Flow Diagramming Mechanics
Data Store
Depicts data at rest
May represent data in:
File folder
Computer-based file
Notebook
Drawn as a rectangle with the right hand vertical line missing
Label includes name of the store as well as the number
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Data Flow Diagramming Mechanics
Process
Depicts work or action performed on data so that they are transformed, stored or distributed
Drawn as a rectangle with rounded corners
Number of process as well as name are recorded
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Data Flow Diagramming Mechanics
Source/Sink
Depicts the origin and/or destination of the data
Sometimes referred to as an external entity
Drawn as a square symbol
Name states what the external agent is
Because they are external, many characteristics are not of interest to us
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Data Flow Diagramming Definitions
Context Diagram
A data flow diagram (DFD) of the scope of an organizational system that shows the system boundaries, external entities that interact with the system and the major information flows between the entities and the system
Level-O Diagram
A data flow diagrams (DFD) that represents a system’s major processes, data flows and data stores at a higher level
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Developing DFDs: An Example
Hoosier Burger’s automated food ordering system
Context Diagram contains no data stores
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Developing DFDs: An Example
Next step is to expand the context diagram to show the breakdown of processes
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Data Flow Diagramming Rules
Basic rules that apply to all DFDs
Inputs to a process are always different than outputs
Objects always have a unique name
In order to keep the diagram uncluttered, you can repeat data stores and data flows on a diagram
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Data Flow Diagramming Rules
Process
No process can have only outputs (a miracle)
No process can have only inputs (black hole)
A process has a verb phrase label
Data Store
Data cannot be moved from one store to another
Data cannot move from an outside source to a data store
Data cannot move directly from a data store to a data sink
Data store has a noun phrase label
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Data Flow Diagramming Rules
Source/Sink
Data cannot move directly from a source to a sink
A source/sink has a noun phrase label
Data Flow
A data flow has only one direction of flow between symbols
A fork means that exactly the same data go from a common location to two or more processes, data stores or sources/sinks
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Data Flow Diagramming Rules
Data Flow (Continued)
A join means that exactly the same data come from any two or more different processes, data stores or sources/sinks to a common location
A data flow cannot go directly back to the same process it leaves
A data flow to a data store means update
A data flow from a data store means retrieve or use
A data flow has a noun phrase label
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Decomposition of DFDs
Functional decomposition
Act of going from one single system to many component processes
Repetitive procedure
Lowest level is called a primitive DFD
Level-N Diagrams
A DFD that is the result of n nested decompositions of a series of subprocesses from a process on a level-0 diagram
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Balancing DFDs
When decomposing a DFD, you must conserve inputs to and outputs from a process at the next level of decomposition
This is called balancing
Example: Hoosier Burgers
In Figure 5-4, notice that there is one input to the system, the customer order
Three outputs:
Customer receipt
Food order
Management reports
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Balancing DFDs
Example (Continued)
Notice Figure 5-5. We have the same inputs and outputs
No new inputs or outputs have been introduced
We can say that the context diagram and level-0 DFD are balanced
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Balancing DFDs:
An Unbalanced Example
In context diagram, we have one input to the system, A and one output, B
Level-0 diagram has one additional data flow, C
These DFDs are not balanced
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Balancing DFDs
We can split a data flow into separate data flows on a lower-level diagram
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Balancing DFDs:
Four Additional Advanced Rules
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Guidelines for Drawing DFDs
Completeness
DFD must include all components necessary for system
Each component must be fully described in the project dictionary or CASE repository
Consistency
The extent to which information contained on one level of a set of nested DFDs is also included on other levels
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Guidelines for Drawing DFDs
Timing
Time is not represented well on DFDs
Best to draw DFDs as if the system has never started and will never stop
Iterative Development
Analyst should expect to redraw diagram several times before reaching the closest approximation to the system being modeled
Primitive DFDs
Lowest logical level of decomposition
Decision has to be made when to stop decomposition
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Using DFDs as Analysis Tools
Gap Analysis
The process of discovering discrepancies between two or more sets of data flow diagrams or discrepancies within a single DFD
Inefficiencies in a system can often be identified through DFDs
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Using DFDs in Business Process Reengineering
Example: IBM Credit
Credit approval process required six days before Business Process Reengineering (see Fig 5-12)

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Using DFDs in Business Process Reengineering
After Business Reprocess Engineering, IBM was able to process 100 times the number of transactions in the same amount of time
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Summary
Data flow diagrams (DFD)
Symbols
Rules for creating
Decomposition
Balancing
DFDs for Analysis
DFDs for Business Process Reengineering (BPR)
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Questions
What is a data flow diagram? Why do systems analysts use data flow diagrams?
What is decomposition? What is balancing? How can you determine if DFDs are not balanced?
Explain the convention for naming different levels of data flow diagrams.
How can data flow diagrams be used as analysis tools?
Chapter 10
Structuring System Requirements:
Conceptual Data Modeling

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Learning Objectives
Define key data-modeling terms
Conceptual data model
Entity-Relationship (E-R) diagram
Entity type
Entity instance
Attribute
Candidate key
Multivalued attributes
Relationship
Degree
Cardinality
Associative entity
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Learning Objectives
Ask the right kinds of questions to determine data requirements for an IS
Learn to draw entity-relationship diagrams (ERD)
Review the role of conceptual data modeling in overall design and analysis of an information system
Discuss relationships and associative entities
Discuss relationship between data modeling and process modeling
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Conceptual Data Modeling
Representation of organizational data
Purpose is to show rules about the meaning and interrelationships among data
Entity-Relationship (E-R) diagrams are commonly used to show how data are organized
Main goal of conceptual data modeling is to create accurate E-R diagrams
Methods such as interviewing, questionnaires and JAD are used to collect information
Consistency must be maintained between process flow, decision logic and data modeling descriptions
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Process of Conceptual Data Modeling
First step is to develop a data model for the system being replaced
Next, a new conceptual data model is built that includes all the requirements of the new system
In the design stage, the conceptual data model is translated into a physical design
Project repository links all design and data modeling steps performed during SDLC
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Deliverables and Outcomes
Primary deliverable is the entity-relationship diagram
There may be as many as 4 E-R diagrams produced and analyzed during conceptual dat