Chapter 3, Activity Diagrams

1. Chapter 3,Activity Diagrams

2. What is UML? • UML (Unified Modeling Language) • Nonproprietary standard for modeling software systems, OMG • Convergence of notations used in object-oriented methods • OMT (James Rumbaugh and collegues) • Booch (Grady Booch) • OOSE (Ivar Jacobson) • Current Version: UML 2.2 • Information at the OMG portal http://www.uml.org/ • Commercial tools: Rational (IBM),Together (Borland), Visual Architect (business processes, BCD) • Open Source tools: ArgoUML, StarUML, Umbrello, LucidChart • Commercial and Opensource: PoseidonUML (Gentleware)

3. Developed the Booch method (“clouds”), ACM Fellow 1995, and IBM Fellow 2003 http://www.booch.com/ 25 year at GE Research, where he developed OMT, joined (IBM) Rational in 1994, CASE tool OMTool At Ericsson until 1994, developed use cases and the CASE tool Objectory, at IBM Rational since 1995, http://www.ivarjacobson.com What is UML? Unified Modeling Language • Convergence of different notations used in object-oriented methods, mainly • OMT (James Rumbaugh and collegues), OOSE (Ivar Jacobson), Booch (Grady Booch) • They also developed the Rational Unified Process, which became the Unified Process in 1999

4. UML: First Pass • You can model 80% of most problems by using about 20% UML • We teach you those 20% • 80-20 rule: Pareto principle: For many events, roughly 80% of the effects come from 20% of the causes. Vilfredo Pareto, 1848-1923 Introduced the concept of Pareto Efficiency, Founder of the field of microeconomics.

5. UML Core Conventions • All UML Diagrams denote graphs of nodes and edges • Nodes are entities and drawn as rectangles or ovals • Rectangles denote classes or instances • Ovals denote functions • Names of Classes are not underlined • SimpleWatch • Firefighter • Names of Instances are underlined • myWatch:SimpleWatch • Joe:Firefighter • An edge between two nodes denotes a relationship between the corresponding entities

6. Outline of this Class • Activity diagrams • Describe the dynamic behavior of a system, in particular the workflow. • Class diagrams • Describe the static structure of the system: Objects, attributes, associations • Use case diagrams • Describe the functional behavior of the system as seen by the user • Sequence diagrams • Describe the dynamic behavior between objects of the system • Statechart diagrams • Describe the dynamic behavior of an individual object

7. UML Activity Diagrams: Activities and Actions An activity is a non-atomic task or procedure decomposable into actions. An action is a task or procedure that cannot be broken into parts. Actions and activities can be anything that humans, machines, organizations, or other entitites do.

8. Activity Graph Elements initial node action node activity symbol activity edge activity final node

9. UML Activity Diagrams • An activity diagram is a special case of a state chart diagram • The states are activities (“functions”) • An activity diagram is useful to depict the workflow in a system.

10. Branching Nodes merge node guards decision node

11. Execution Model • Execution is modeled by tokens that are produced by action nodes, travel over action edges, and are consumed by action nodes. • When there is a token on every incoming edge of an action node, it consumes them and begins execution. • When an action node completes execution, it produces tokens on each of its outgoing edges. • An initial node produces a token on each outgoing edge when an activity begins. • An activity final node consumes a token available on any incoming edge and terminates the activity.

12. Branching Execution Decision and merge node behavior: • If a token is made available on the incoming edge of a decision node, the token is made available on the outgoing edge whose guard is true. • If a token is available on any incoming edge of a merge node, it is made available on its outgoing edge. • Guards must be mutually exclusive.

13. Deadlock RunDrier cannot execute: when the activity begins, there is a token on the edge from the initial node but not on the other incoming edge.

14. Forking and Joining Nodes fork node join node

15. Forking and Joining Execution • A token available on the incoming edge of a fork node is reproduced and made available on all its outgoing edges. • When tokens are available on every incoming edge of a join node, a token is made available on its outgoing edge. • Concurrency can be modeled without these nodes.

16. Concurrent Problem Solution (An example)

17. Object Nodes Data and objects are shown as object nodes. object node state object node

18. Control and Data Flows • Control tokens do not contain data, data tokens do. • A control flow is an activity edge that is a conduit for control tokens. • A data flow is an activity edge that is a conduit for data tokens. • Rules for token flow through nodes apply to both control and data tokens, except that data is extracted from consumed tokens and added to produced tokens.

19. Control and Data Flow Example control flow data flows control flow

20. Activity Parameters • Activity parameters are object nodes placed on activity symbol boundaries to indicate data or object inputs or outputs. • Activity parameters contain the data or object name. • Activity parameter types are specified in the activity symbol beneath the activity name.

21. Activity Parameter Example: Maximum Finding Algorithm activity parameter types input activity parameter output activity parameter

22. Activity Diagram Heuristics • Flow control and objects down the page and left to right. • Name activities and actions with verb phrases. • Name object nodes with noun phrases. • Don’t use both control and data flows when a data flow alone can do the job. • Make sure that all nodes entering an action node can provide tokens concurrently (to prevent deadlocks). • Use the [else] guard at every branch.

23. When to Use Activity Diagrams When making a dynamic model of any process. • Design processes (what designers do) • Designed processes (what designers create) • During analysis • During resolution

24. Activity Diagrams allow to model Decisions Decision

25. Activity Diagrams can model Concurrency • Synchronization of multiple activities • Splitting the flow of control into multiple threads Splitting Synchronization

26. Activity Diagrams: Grouping of Activities • Activities may be grouped into swimlanes to denote the object or subsystem that implements the activities. Dispatcher Allocate Resources Open Coordinate Archive Incident Resources Incident FieldOfficer Document Incident

27. Activity Diagram vs. Statechart Diagram Statechart Diagram for Incident Focus on the set of attributes of a single abstraction (object, system) Event causes state transition Closed Active Inactive Archived Incident- Documented Incident- Archived Incident- Handled Activity Diagram for Incident (Focus on dataflow in a system) Triggerless transition Completion of activity causes state transition

28. Example of an Activity Diagram with a Frame

29. The Activity Diagram without Frame

30. Activity Diagram Example Action Object node

31. Activity Diagram: Activity Nodes & Edges • An activity diagram consists of nodes and edges • There are three types of activity nodes • Control nodes • Executable nodes • Most prominent: Action • Object nodes • E.g. a document • An edge is a directed connection between nodes • There are two types of edges • Control flow edges • Object flow edges

32. Activity Diagram Example Control flow Object flow

33. Summary: Activity Diagram Example Fork node Join node Merge node Initial node Control flow Final node Action Object node Object flow

34. Example 1: What the diagram represents? • A document • A printer • A word-processor • A user of a word-processor • A page being printed • The diagram is invalid

35. Example 2: What is the max number of concurrent threads that is possible? • 1 • 2 • 3 • 4 • 5

36. Example 3: In this diagram... • Fill Order is executed before Receive Payment • Overnight Delivery is executed in parallel with Regulary Delivery • Close Order is executed after Receive Payment • Fill Order is executed in parallel with Send Invoice • Send Invoice is possibly executed • Regular Delivery is always executed

37. Example 4:

38. Example 5: Cash Withdrawal Process from a Bank

39. Example 6: Passenger to Airplane There should be only one final node, not two!!!

40. Alıştırma (10 dakika) Müşteri restorana girer. Eğer oturacak yer varsa oturur, yoksa çıkar. Oturduktan sonra menüye bakar. İki seçeneği vardır: Çin yemeği, Japon yemeği. İkisini de yemek istemiyorsa çıkar gider. İstediği yemeği seçer, garsona söyler. Garson mutfağa siparişi geçer. Yemekler hazır olduğunda garson yemeği müşteriye götürür. Müşteri yemeği yedikten sonra hesap ister. Eğer memnun kaldıysa hesabı ödeyip bahşiş bırakır. Eğer memnun kalmadıysa hesabı öder, bahşiş bırakmadan restorandan çıkar.

41. Summary • A process is a collection of related tasks that transforms a set of inputs to a set of outputs. • UML activity diagrams model processes by depicting actions and the flow of control and data between them. • Activity symbols contain activity graphs consisting of • action nodes • action edges • data nodes • special nodes for starting and stopping activities, branching, forking, and joining • Activity diagrams can represent any process and are useful throughout software design.

42. Another view on UML Diagrams