- uses various symbols to show how the system transforms input data into useful information
- shows how data moves through an information system but does not show program logic or processing steps
- provides a logical model that shows what the system does, not how it does it
- subdivided into successively lower levels in order to
provide increasing amounts of detail.
Data Flow Diagram
CONTEXT DIAGRAM
Highest level (most general)
Purpose: shows inputs and outputs of the system
Only one process symbol
LOWER-LEVEL DIAGRAMS (Level – 0, …)
Purpose: show all major activity steps of a system
Processes are labeled 1.0, 2.0 and so on
Data Flow Diagram Symbols
Gane and Sarson Symbols
Yourdon-Coad Symbols
- source or destination of a data flow which is outside the area of study. (Terminators, Source, Sink)
- Only those entities which originate or receive data are
represented on a business process diagram. - symbol used is an oval containing a meaningful and unique identifier.
Data Flow Diagram Symbols –External Entity
- process shows a transformation or manipulation of data flows
within the system. Receives input data and produces output that
has a different content, form, or both - Contain the business logic, also called business rules. Referred to as a black box
- The symbol contains two descriptive elements:
An identification number appears in the top part to show the process number
A descriptive title is placed in the center of the box. This should be a
simple imperative sentence with a specific verb, for example ‘maintain customer records’ or ‘find driver’.
Data Flow Diagram Symbols –
Process
Common DFD Mistakes
Illegal data flows
Black Hole
Miracle / Spontaneous Generation
Grey Hole
Same names for the data flows, data stores, processes, and
entities
shows the flow of information from its source to its
destination.
- represented by a line, with arrowheads showing the
direction of flow. Information always flows to or from a process
and may be written or electronic.
data Flow Diagram – Data Flow
Documents the details of a functional primitive, and represents
a specific set of processing steps and business logic
Process Description
Process Description Tools
Modular Design
Structured English
Decision Tables
Decision Trees
based on combinations of three logical structures, sometimes called __________, which serve as building blocks for the process
control structures
Modular Design
a subset of standard English that shows the iteration structure and describes logical processes clearly and accurately
Structured English
logical structure that shows every combination of conditions and outcomes
Decision Tables
graphical representation of the conditions, actions, and rules found in a decision table
Decision Trees
model shows how the system’s requirements are
implemented
physical model
central documentation tool for structured analysis
data dictionary
can be used to develop a logical model during one systems analysis phase, and a physical model during the systems design phase
Structured analysis tools
A model of software deployment where an application is hosted as a service provided to customers over the Internet.
- reduces the customer’s need for software maintenance, operation, and support
___________ believes that the concept of software as a service is redefining the way that
companies develop and deploy their information systems
Software as a Service
The Software and Information Industry Association (SIIA)
- System design is influenced by compatibility issues
Systems are designed to run on local and wide-area company networks
Web-based features are treated as enhancements rather than core elements of the
design
Traditional development
Systems are developed and delivered in an Internet-based framework such as .NET or
WebSphere
Internet-based development treats the Web as the platform, rather than just a
communication channel
Web-based software usually requires additional layers, called middleware
Web-based development
The transfer of information systems development, operation, or maintenance to an outside firm that provides these services, for a
fee, on a temporary or long-term basis
can refer to relatively minor programming tasks,
renting software from a service provider, outsourcing a basic
business process (often called business process outsourcing, or
BPO), or handling a company’s entire IT function
outsourcing
A firm that offers outsourcing solutions is called a ______________
service provider
Also called managed hosting
Internet business services (IBS)
also known as global outsourcing
Practice of shifting IT development, support, and operations to other countries
Offshore Outsourcing
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Unit 1: Information Technology in Basics4
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Unit 2: Components of a Computer System55
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Unit 3: Computer Types and Varieties11
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Unit 4: Evolution of a Computer27
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Unit 5: Information Technology and Emerging Trends43
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Unit 6: Information Systems32
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Unit 7: Systems Development Life Cycle88
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Unit 7 (1)43
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FINALS: UNIT 10 - CYBERCRIME52
