Modeling Processes and Logic

1. Modeling Processes and Logic

2. Where are we?

3. Modeling Processes and Logic Process vs. Data centric view Structured Analysis vs. Information Engineering Where you start not what you do We have some descriptions of the processes Interviews, surveys, fact finding, etc. Graphical representation Logical vs. Physical What vs. How What we�d like to happen vs. What�s actually happening Implementation independent

4. The Apple Get the apple Get the peeling device Wash the apple Hold the apple Peel the apple with the peeling device Discard peel Process the apple into the desired form. Get the apple by removing it from the fruit drawer in the refrigerator. Get the paring knife from the upper left-hand kitchen drawer. Wash the apple under the kitchen faucet using a scrubbing action with your hands. Hold the apple in your leftt (opposite if right handed) Peel the apple with the knife with blade pointing towards you. Discard the peel into a suitable garbage container Eat the apple by biting down on a portion of the apple with your mouth and chewing.

5. Benefits of Logical Modeling First Less premature commitment to technology My kitchen, my knife Tends to reduce overlooking fundamental steps/processes/requirements Good communication tools with stake holders 1000 words Move away from the way the current system does tasks but think about what tasks it does. Do we always eat the apple?

6. Data Flow Diagrams (DFD) Data in motion � data flows Reports, phone calls, order forms .. Data at rest � data stores Access database, shoebox, my brain Data transformation � Processes Man, machine, computer Data Users � External Entities Users, other systems, other organizations Source or Sink

7. DFD: Peeling an Apple

8. Finding Logical Processes: 4 Types Data flows in and is used to create an output calculation to datastore, input to process, or entity Data is verified but not manipulated Passwords, bank account # Data is re-organized Sorted, filtered Data is routed based on some properties Is a person an entity or a process?

9. DFD Hierarchy DFD�s done in levels Like outlining a paper Context Diagram What is and is not in the system? Level-0 DFD Major processes and sequence maintains in or outflow of datastore directly responsible for distribution with source/sink entities captures data from source entity high level descriptors of more complicated data transformation Level-1 through Level-n DFDs Generally a max of 7 levels

10. Context Diagram

11. Level-0 DFD

12. Level-1 DFD

13. Part of Level-2 (n) DFD �functional primitive�

14. Rules for DFDs A child cannot received different input or produce different output relative to parent A process cannot have only outputs � �Miracle.� A process cannot have only inputs � �Black Hole.� The inputs to a process must be sufficient to produce the outputs from the process - (Gray Hole). All data stores must be connected to at least one process. A data store cannot be connected to a source or sink. A data flow can have only one direction of flow. Multiple data flows to and/or from the same process and data store must be shown by separate arrows. If the exact same data flows to two separate processes, it should be represented by a forked arrow. Data cannot flow directly back into the process it has just left. All data flows must be named using a noun phrase

15. Visual Cues

16. DFDs vs. Flowcharts System flowcharts graphically depict programs, inputs, outputs, and data storage activities. Appear to be logical in nature, actually depict the physical details of the system Much more focused on order of steps

17. Modeling Process Logic DFD gives us a way to verify system processes End users, analysts, BPR Verify against system requirements We also need models of what goes on inside a process Structured English, Decision Table, Decision Tree, State-Transition Diagram A logical model vs. models of logic

18. Structured English Active tone Repetition, Decision, Sequence One entrance One exit If a problem, then decompose

19. Decision Table

20. Decision Tree

21. State-Transition Diagram

22. Process Logic Tool Comparison

23. Step 1: A system context diagram is constructed to establish initial project scope. Step 2: A functional decomposition diagram is drawn to partition the system into logical subsystems and/or functions. Step 3: An event-response list is compiled to identify and confirm the business events to which the system must provide a response. Step 4: One process, called an event handler is added to the decomposition diagram for each event. Step 5: An event diagram is constructed and validated for each event. Step 6: A system diagram(s) is constructed by merging the event diagrams. Step 7: A primitive diagram is constructed for each event process. These data flow diagrams show all of the elementary processes, data stores, and data flows for single events. Process Modeling No additional notes provided. . .No additional notes provided. . .

24. Figure 6.18 Event-Driven Process Modeling Strategy - slide 1 No additional notes provided. Figure 6.18 Event-Driven Process Modeling Strategy - slide 1 No additional notes provided.

25. Figure 6.18 Event-Driven Process Modeling Strategy - slide 2 No additional notes provided. Figure 6.18 Event-Driven Process Modeling Strategy - slide 2 No additional notes provided.

26. Conclusion None of these tools guarantee that you�ve documented the right process Good for communication Avoid focus on current system physical processes Avoid focus on proposed system technical solutions