CALCULATE GROSS PAY has no outputs and is called a black hole process. APPLY INSURANCE PREMIUM has no input and is called a spontaneous generation process.
Must have at least one input and at least one outputContains business logic that transforms the dataProcess name identifies its function (verb)Process number does not signify precedenceExamples: print bill or add customerĭata flow symbolRepresents one or more data itemsThe symbol for a data flow is a line with a single or double arrowheadFIGURE 5-5 Examples of correct combinations of data flow and process symbols89Data Flow Diagrams (Cont.)Data flow symbolSpontaneous generation (Process must act on input)Black holesGray holesFIGURE 5-6 Examples of incorrect combinations of data flow and process symbols.
DATA AND PROCESS MODELING TOOLS HOW TO
Systems Analysis and Design 10th EditionTopic 4Data and Process Modeling1Describe data and process modeling concepts and tools, including data flow diagrams, a data dictionary, and process descriptionsDescribe the symbols used in data flow diagrams and explain the rules for their useDraw data flow diagrams in a sequence, from general to specific2Chapter Objectives 2Explain how to level and balance a set of data flow diagramsDescribe how a data dictionary is used and what it containsUse process description tools, including structured English, decision tables, and decision treesDescribe the relationship between logical and physical models3Chapter Objectives (Cont.)34Overview of Data and Process Modeling ToolsSystems analysts use many graphical techniques to describe an information systemA data flow diagram (DFD) uses various symbols to show how the system transforms input data into useful information45Data Flow DiagramsA data flow diagram (DFD) shows how data moves through an information system but does not show program logic or processing stepsA set of DFDs provides a logical model that shows what the system does, not how it does it56Data Flow Diagrams (Cont.)FIGURE 5-3 Data flow diagram symbols, symbol names, and examples of the Gane and Sarson and Yourdon symbol setsDFD SymbolsFour basic symbolsGane & Sarson used in textYourdon also popularĦ7Data Flow Diagrams (Cont.)Process Symbol
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