lec6-1 - MIE 350 Data Flow Diagrams Michael Gruninger...

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MIE350: Software Development Methodologies 1 MIE 350 Data Flow Diagrams Michael Gruninger Information Engineering Centre gruninger@mie.utoronto.ca
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MIE350: Software Development Methodologies 2 Outline • DFDs are hierarchical – Context level, Level 0, Level 1, … • How to build DFDs – Context Diagram – DFD fragments – Level 0 Diagram – Level k Diagrams, k > 0 – Validating
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MIE350: Software Development Methodologies 3 Readings • Textbook Ch 5 (or Ch 6 in the 3rd edition) – “Using Data Flow Diagrams to Define Business Processes” – “Creating Data Flow Diagrams” – “Applying the Concept at CD Selections” – Not: “Process Descriptions”
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The System
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Level 1 DFD For Process 1 Level 1 DFD For Process 2 Level 1 DFD For Process 3 Level 2 DFD For Process 1.1 Level 2 DFD For Process 1.2
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MIE350: Software Development Methodologies 7 DFD Hierarchy • Context Diagram is at the top – “system” is a single process (Process 0) – Include external entities – Only one context level diagram • Level 0 – Expand Process 0 to a set of processes, data flows, and data stores – Only one level 0 diagram
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MIE350: Software Development Methodologies 9 DFD Hierarchy • Level 1 – Decompose each process at level 0 – Usually as many level 1 diagrams as level 0 processes • Level 2 – Expand each level 1 process • Level k – Keep going …
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MIE350: Software Development Methodologies 10 DFD Principles • Business processes are decomposed via the hierarchy • Balancing – All information at one level is accurately represented on the next one down • E.g., a data flow leaving a process at level k must be present at level k+1
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MIE350: Software Development Methodologies 12 DFD Questions • Questions so far?
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lec6-1 - MIE 350 Data Flow Diagrams Michael Gruninger...

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