1. Software Engineering
Chapter 5 (Part 3)
System Modeling
Dr.Doaa Sami

2. 2
D. Behavioral Models

3. 3
1. Activity Diagrams

4. Activity Diagram  An activity diagram is a Data-driven Model.4
 An activity diagram is a Data-driven Model.
 An activity diagram is used to display the sequence of activities.
 Activity diagrams show the workflow from a start point to the finish point, include details of many decision paths that exist in progression of events contained in the activity.
 They may be used to detail situations where parallel processing may occur in the execution of some activities.

5. Activity elements that make up the activity.5
 Activity: it is shown as a round-cornered rectangle enclosing all the actions, control flows and other
elements that make up the activity.

6. Action 6
 An Action represents a single step within an activity. Actions are denoted by round-cornered
rectangles.
Perform an
action

7. Control Flow arrowhead.7
 A Control Flow shows the flow of control from one action to the next. Its notation is a line with an
arrowhead.
Send Accept
payment payment

8. Initial Node 8
 An Initial or Start Node is depicted by a large black spot, i.e. filled circle.
action

9. Final Node 9
 There are two types of Final Node:
The Activity Final Node is depicted as an empty circle with a dot inside it. It denotes the end of all control flows within the activity.
The Flow Final Node is depicted as an empty circle with a cross inside it. It denotes the end of a single control flow.

10. Decision and Merge Nodes10
 Decision Nodes and Merge Nodes have the same notation: a diamond shape but with opposite directions of arrowheads. They can both be named.
 The control flows coming away from a decision node will have guard conditions which will allow control to flow if the guard condition is met.

11. Fork and Join horizontal or vertical bar (dependent on whether the11
 Forks and Joins have the same notation: either a
horizontal or vertical bar (dependent on whether the
control flow is running left to right or top to bottom).
 They indicate the start and end of concurrent threads
of control.
 Fork: denotes the beginning of parallel activity.
 Join: denotes the end of parallel processing.

12. Example: Creating Document Activity12
Open the word processing package.
Create a file.
Save the file under a unique name within its directory.
Type the document.
If graphics are necessary, open the graphics package, create the graphics, and paste the graphics into the document.
If a spreadsheet is necessary, open the spreadsheet package, create the spreadsheet, and paste the spreadsheet into the document
Save the file.
Print a hard copy of the document.
Exit the word processing package.

13. Solution 13

14. 14
2. State Diagrams

15. State Diagrams  A State diagram is an Event-driven Model.15
 A State diagram is an Event-driven Model.
 State diagrams show system states and events that cause transitions from one state to another.
 State diagrams do not show the flow of data within the system but may include additional information on the computations carried out in each state.

16. State Diagrams Cont. 16
 In UML state diagrams, rounded rectangles represent System States.
 They may include a brief description (following ‘do’) of the actions taken in that state.
 The labeled arrows represent Stimuli that force a transition from one state to another.
 Start and End States indicated by using filled circles, as in the activity diagrams.

17. State Diagram Example  A very simple microwave oven system: 17
 The microwave has a switch to select full or half power, a numeric keypad to input time, a start/stop button, and an alphanumeric display.
 We assumed that the sequence of actions using the microwave is:
1. Select the power level (either half power or full power).
2. Input the cooking time using a numeric keypad.
3. Press Start and the food is cooked for the given time.
 For safety reasons, oven should not operate when door is open.

18. Solution 18

19. Model-Driven Engineering19
 Model-Driven Engineering (MDE): is an approach to software development where models rather than programs are principal outputs of development process.
Programs that execute on a hardware/software platform are then generated automatically from the models.
 Proponents of MDE argue that this raises the level of
abstraction in SWE, so that engineers no longer have to be concerned with programming language details.

20. Model Driven Architecture20
 Models at different levels of abstraction are created. From a high-level, platform independent model, it is possible, to generate a working program without manual intervention.
 Model-driven engineering (MDE) has its roots in model- driven architecture (MDA).
 MDA focuses on the design and implementation stages of software development whereas MDE is concerned with all aspects of the software engineering process.

21. Summery and external actors; sequence diagrams add more21
 A model is an abstract view of a system that ignores system details. Complementary system models can be developed to show the system’s context, interactions, structure and behaviour.
 Use case diagrams and sequence diagrams are used to describe the interactions between users and systems in the system being designed.
 Use cases describe interactions between a system
and external actors; sequence diagrams add more
information to these by showing interactions between system objects.

22. Summery 22
 Class diagram is used to define the static structure of classes in a system and their associations.
 Activity diagrams maybe used to model processing of data, where each activity represents one process step.
 A State diagrams show system states and events that cause transitions from one state to another.
 Model-driven engineering is an approach to SW development in which a system is represented as a set of models that automatically transformed to executable code.

23. Reference 23
 Fowler, Martin. UML distilled. Addison-Wesley Professional, 2004.
 Schmuller, Joseph. Sams teach yourself UML in
24 hours. Sams publishing, 2004. 
ntroduction_to_uml_sequence_diagrams/ 
utorial/