 Chapter 5 System Modeling 1

Context Model  Shows context (environment) of proposed system  Other software  People  Roadmap of major areas to consider  Other software systems  Supplying data  Using Data  Sharing data  Offering services  User interface 2

Context 3

Process UML Activity Diagram  Show activities of a system  Symbology  Filled circle – start of a process  Rounded boxes – activities  Arrows - flow  Bars –  Full completion of predecessors needed  successors occur in parallel 4

Process – UML Activity Diag. 5

Use Case Modeling  Each use case is a discrete task  Actors (stick figures)  People  Programs  Activity  Tabular description 6

Use Case 7

Use Case - textual 8 MHC-PMS: Transfer data ActorsMedical receptionist, patient records system (PRS) DescriptionA receptionist may transfer data from the MHC-PMS to a general patient record database that is maintained by a health authority. The information transferred may either be updated personal information (address, phone number, etc.) or a summary of the patient’s diagnosis and treatment. DataPatient’s personal information, treatment summary StimulusUser command issued by medical receptionist ResponseConfirmation that PRS has been updated CommentsThe receptionist must have appropriate security permissions to access the patient information and the PRS.

Use - Case Chapter 4 Requirements engineering9

Sequence Diagrams  Actors, objects in boxes at top  Dotted line denotes their timeline  Solid box denotes their activity  Arrows show interaction between activities  Time flow is top to bottom 10

Sequence Diagam Chapter 4 Requirements engineering11

12 Sequence Diagram

Sequence Diagrams  Web server access  Three tier model  FTP protocol  DHCP - Broadcast, Offer, Request, Acceptance  Web access/DNS Chapter 4 Requirements engineering13

Activity  Home security system  Window, door sensors  Central security system  Phone confirmation  Dispatch  Security officer Chapter 4 Requirements engineering14

Class Diagrams  Define objects and object relationships  Box refers to a class  Line designates a relationship  Numbers identify quantity  1 – single  * many 15

Class Diagrams Chapter 4 Requirements engineering16

Class Detail  Name at top  Attributes next  Methods at bottom 17

Class Detail Chapter 4 Requirements engineering18

Generalization hierarchy  Class hierarchy  Root represents base class, most common definition  Branches add attributes, operations 19

Class Hierarchy 20

Class Hierarchy - detailed 21

Example  Real Estate  Property  Residential  Commercial  Land Chapter 4 Requirements engineering22

Data Driven Modeling  Processes are driven by data that arrives  UML Activity Diagram Chapter 4 Requirements engineering23

Data Driven Modeling Chapter 4 Requirements engineering24

Event Driven Modeling  Models behavior in response to events  Especially in real-time and embedded control systems Chapter 4 Requirements engineering25

State Diagrams  Model event driven process  Notation  Circles  indicate states  May indicate action  Arcs  indicate event trigger  may indicate output Chapter 4 Requirements engineering26

State Diagram Example Chapter 4 Requirements engineering27

States Chapter 4 Requirements engineering28 StateDescription WaitingThe oven is waiting for input. The display shows the current time. Half powerThe oven power is set to 300 watts. The display shows ‘Half power’. Full powerThe oven power is set to 600 watts. The display shows ‘Full power’. Set timeThe cooking time is set to the user’s input value. The display shows the cooking time selected and is updated as the time is set. DisabledOven operation is disabled for safety. Interior oven light is on. Display shows ‘Not ready’. EnabledOven operation is enabled. Interior oven light is off. Display shows ‘Ready to cook’. OperationOven in operation. Interior oven light is on. Display shows the timer countdown. On completion of cooking, the buzzer is sounded for five seconds. Oven light is on. Display shows ‘Cooking complete’ while buzzer is sounding.

Events Chapter 4 Requirements engineering29 StimulusDescription Half powerThe user has pressed the half-power button. Full powerThe user has pressed the full-power button. TimerThe user has pressed one of the timer buttons. NumberThe user has pressed a numeric key. Door openThe oven door switch is not closed. Door closedThe oven door switch is closed. StartThe user has pressed the Start button. CancelThe user has pressed the Cancel button.

State Diagram  Graph structure  Can be characterized in tables – row contain  State, trigger, new state Chapter 4 Requirements engineering30

State Diagrams - Examples  Fax decoding  Data driven  Printer console  Driven by buttons, internal sensors  Power Plant Control System  Stopwatch  Stop, start  Lap time Chapter 4 Requirements engineering31

Example  Alarm clock  Three buttons  Set time  Set alarms  Enable/disable alarm  Change display – clock or alarm time  Power Failure Chapter 4 Requirements engineering32

Model Driven Engineering  Developer defines model  Implementation is automatically generated  Not in widespread use Chapter 4 Requirements engineering33