ISOM221+Lecture+7+-+Process+Modeling+II

ISOM221+Lecture+7+-+Process+Modeling+II - ISOM221...

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ISOM221 Information Systems Analysis and Design Lecture 7: Process Modeling II 1 Last Class You have learned Key elements of DFD The concept of process decomposition How to construct context diagram How to construct context diagrams 2
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Agenda Learn how to further develop context diagrams into lower-level DFDs Learn how to validate DFDs 3 Steps in Building DFDs 1. Build the context diagram 2. Identify major processes o Read the text to identify and underline ‘candidate’ processes, (usually verbs) describing some ways in which data are manipulated t Reread the text to identify incoming and outgoing data flows for each process. Then do the same for external entities and data stores 3. Create DFD fragments for each major process 4. Organize DFD fragments into level 0 diagram 5. Decompose level 0 processes into level 1 diagrams as needed; decompose level 1 processes into level 2 diagrams as needed; etc. 6. Validate DFDs with user to ensure completeness and correctness 7. Iterate as needed 4
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Creating the Context Diagram Draw one process representing the entire system (process 0) Find all inputs and outputs that come from or go to external entities; draw as data flow go to external entities; draw as data flows Draw in external entities as the source or destination of the data flows 5 Sample Scenario – Tune Source Digital Music Download System Three key requirements Search and Browse Purchase Promote 6
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Context Diagram 7 Creating DFD Fragments Each major requirement is converted into one DFD fragment Number the process and change its name into verb phrase Add data flows to show use of data stores as sources and destinations of data Layouts typically place processes in the center inputs from the left outputs to the right stores beneath the processes 8
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Customers can search for tunes based on title, artist, or genre of music. Customers may select tunes for several purposes. First, they may select tunes to listen to samples. The system automatically adds those selected tunes to an “Interests list” that tracks each customer’s interests. Second, they may select tunes to add to their “Favorites list” by themselves. Finally, they may select tunes to purchase and download. If the customer has visited the site and created entries on a Favorites list, the display of tunes on the site will be tailored to the customer’s favorites. Targeted promotions are sent to registered customers when they visit the site to search and browse tunes. 9
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ISOM221+Lecture+7+-+Process+Modeling+II - ISOM221...

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