DT249/4 Information Systems Engineering

1. DT249/4 Information Systems Engineering Systems Modelling

2. Diagrams • Context Diagram • Data Flow Diagram • Activity Diagram • Use Case Diagram • Class Diagram

3. Context Diagram

4. Context Diagram • One of the first things you need to do when specifying a system is to decide on the system boundaries. • This means deciding what functionality should be included in the system and what is provided by the system’s environment.

5. Context Diagram • You should look at possible overlaps in functionality with existing systems and decide where new functionality should be implemented. • These decisions should be made early in the process to limit the system costs and the time.

6. Context Diagram Other System 1 Other System 3 Other System 5 The System we are developing Other System 4 Other System 6 Other System 2

7. Context Diagram ATM Machine

8. Data Flow Diagram

9. Data Flow Diagram • Used to show end-to-end processing in a system • DFDs show the entire sequence of actions that take place from an input being processed to the corresponding output that is the system’s response.

10. Data Flow Diagram Sink External Entities Source

11. Data Flow Diagram Sink External Entities An outside system that sends or receives data, communicating with the system being diagrammed. Source

12. Data Flow Diagram Data Flow

13. Data Flow Diagram Data Flow The route that data takes between the external entities, processes and data stores.

14. Data Flow Diagram Process

15. Data Flow Diagram Process A process is anything that changes the data, to produce an output.

16. Data Flow Diagram Data Store

17. Data Flow Diagram Data Store Files or repositories that hold information for later use, such as a database table or a membership form.

18. Data Flow Diagram Process Source Sink Data Store Data Flow

19. Data Flow Diagram Process Data Flow Source Sink Data Store

20. Data Flow Diagram

21. Data Flow Diagram A CUSTOMER orders food, and that process returns a bill to the customer. The order goes to the KITCHEN. The process of ordering the food, also sends inventory details to the INVENTORY database and the order to the ORDER database. The INVENTORY database sends inventory details onto a Generate Reports process, which also receives the order from the ORDER database. The Generate Reports process sends a Report to the MANAGER who sends the inventory order to the Order Inventory process, and that process sends the inventory details back to the INVENTORY database, and sends the inventory order to the SUPPLIER.

22. Data Flow Diagram A CUSTOMER(EXTERNAL ENTITY) will ORDER FOOD(PROCESS); The ORDER FOOD process will send an ORDER to the KITCHEN(EXTERNAL ENTITY); The ORDER FOOD process will send an ORDER to the ORDER(DATA STORE); The ORDER FOOD process will send an INVENTORY DETAILS to the INVENTORY(DATA STORE); The INVENTORY data store sends the INVENTORY DETAILS to the GENERATE REPORTS(PROCESS); The ORDER data store sends the ORDER to the GENERATE REPORTS(PROCESS); The GENERATE REPORTS process sends REPORTS to the MANAGER(EXTERNAL ENTITY); The MANAGER external entity sends the INVENTORY ORDER to the ORDER INVENTORY(PROCESS); The ORDER INVENTORY process send INVENTORY DETAIL back to the INVENTORY(DATA STORE); The ORDER INVENTORY process send INVENTORY ORDER to the SUPPLIER(EXTERNAL ENTITY);

23. Data Flow Diagram

24. Data Flow Diagram

25. Data Flow Diagram When renting a video, a CUSTOMER requests a video from the Rent Video process, which sends a bill back to the CUSTOMER. The Rent Video process send rental information to the RENTAL database which sends the rental information onto the Generate Rental Report process, which passes a Rental report onto the MANAGER. When returning a video, a CUSTOMER sends the Video and Rental Information onto the Return Video process, which sends a Return Receipt back to the CUSTOMER. The Return Video process sends Video Information onto the VIDEO LIBRARY database, which sends Video Information back to the Rent Video Process (mentioned previously). The Return Video process also sends Rental information onto the RENTAL database (mentioned previously).

26. Data Flow Diagram A CUSTOMER(EXTERNAL ENTITY) send a VIDEO REQUEST to RENT VIDEO(PROCESS); The RENT VIDEO process will send a BILL to the CUSTOMER(EXTERNAL ENTITY); The RENT VIDEO process will send RENTAL INFO to the RENTAL(DATA STORE); A CUSTOMER(EXTERNAL ENTITY) send VIDEO RENTAL INFO to RETURN VIDEO(PROCESS); The RETURN VIDEO process send a RETURN RECEIPT to the CUSTOMER(EXTERNAL ENTITY); The RETURN VIDEO process send VIDEO INFO to the VIDEO LIBRARY(DATA STORE); The RETURN VIDEO process send RENTAL INFO to the RENTAL(DATA STORE); The VIDEO LIBRARY data store send VIDEO INFO to RENT VIDEO(PROCESS); The RENTAL data store send RENTAL INFO to GENERATE RENTAL REPORT(PROCESS); The GENERATE RENTAL REPORT process sends a RENTAL REPORT to the MANAGER(EXTERNAL ENTITY) ;

27. Data Flow Diagram

28. Data Flow Diagram

29. Activity Diagram

30. Activity Diagram • Process models show the overall process and the processes that are supported by the system.

31. Activity Diagram • We’ll use UML Activity Diagrams to represent process flows.

32. Activity Diagram Start Stop

33. Activity Diagram Start The Start Node is also called the Initial Note. Stop The Stop Node is also called the Final Note.

34. Activity Diagram Condition

35. Activity Diagram Condition The condition defines a guard which must evaluate to true in order to traverse the node.

36. Activity Diagram Action

37. Activity Diagram Action An action may be physical, such as Inspect Forms, or electronic, such as Display Student Screen.

38. Activity Diagram Decision

39. Activity Diagram Decision The flows leaving a decision will normally include conditions

40. Activity Diagram Fork Join

41. Activity Diagram Fork This denotes the beginning of parallel activity. Join All flows going into the join must reach it before processing can continue.

42. Activity Diagram Join Start Action Fork Stop Decision Condition

43. Activity Diagram

44. Activity Diagram

45. Activity Diagram To enrol in college: "Fill out enrolment forms", if they are filled out incorrectly, then if there is help available, "Obtain Help", but if there is no help available, retry to "Fill out enrolment forms". If it's a trivial problem or the form are filled out correctly, proceed to "Enrol in University. Once you've enrolled, two things can happen in parallel; (1) you can "Attend University Overview Presentation", and (2) you can "Enrol in Seminar(s), an "Make initial Tuition Payments".

46. Activity Diagram Fill Out Enrollment Forms IF the forms are filled out incorrectly THEN IF it’s a big problem THEN IF there is help available THEN “Obtain Help” ELSE Return to “Fill Out Enrollment Forms” ELSE it’s a trivial problem so “Enrol in University” ELSE “Enrol in University” Happening in Parallel (Concurrently): Attend university Enrol in Seminar(s)  Make Initial Tuition Payment

47. Activity Diagram

48. Activity Diagram

49. Activity Diagram To buy a ticket: "Show Your Ticket at the Check-In Counter" then "Verify that Ticket". If the Ticket has a problem, "Refer the Passenger to the Customer Services" and exit. Otherwise “Check-in the Luggage”. When "Accepting the Luggage", check if it is “Subject to a Fee”, if it is “Pay Fees”, otherwise don't. In either case “Issue a Boarding Pass” and exit.

50. Activity Diagram Show Your Ticket at the Check-In Counter;  Verify the Ticket; IF the Ticket is NOT OK THEN Refer to CUSTOMER SERVICES;EXIT; END IF; Check in Luggage; Accept Luggage; IF Luggage is Subject to Fee THEN Pay Fee; END IF; Issue Boarding Pass;