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Course Instructor: Aisha Azeem Introduction to UML.

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1 Course Instructor: Aisha Azeem Introduction to UML

2  UML stands for U nified M odeling L anguage.  It is a standard language for specifying, visualizing, constructing, and documenting the artifacts of software systems. Introduction Specifying Visualizing ConstructingDocumenting Business Modeling Communications

3  Class:  Class represents set of objects having similar responsibilities.  Use case:  Use case represents a set of actions performed by a system for a specific goal.  Interaction:  Interaction is defined as a behavior that consists of a group of messages exchanged among elements to accomplish a specific task. UML Building Blocks

4  State machine:  State machine is useful when the state of an object in its life cycle is important.  It defines the sequence of states an object goes through in response to events. Events are external factors responsible for state change.  Note:  A note is used to render comments, constraints etc of an UML element. Cont...

5  Generalization:  Generalization can be defined as a relationship which connects a specialized element with a generalized element. It basically describes inheritance relationship in the world of objects.  Aggregation:  Whole part relationship i.e. large part “whole” contains one or more parts. E.g. building “whole” contains rooms ”parts”  Composition:  Is a relationship in which if the “whole” part dies, the child has to die as well. E.g. if building collapse, rooms no more exist Cont...

6 UML Models, Views, Diagrams  UML is a multi-diagrammatic language  Each diagram is a view into a model  Diagram presented from the aspect of a particular stakeholder  Provides a partial representation of the system  Is semantically consistent with other views  Example views

7 Models, Views, Diagrams

8  UML diagrams are the ultimate output of the entire discussion.  All the elements, relationships are used to make a complete UML diagram and the diagram represents a system.  UML includes the following nine diagrams  Class diagram  Object diagram  Use case diagram  Sequence diagram  Collaboration diagram  Activity diagram  State chart diagram  Deployment diagram  Component diagram UML Diagrams

9  Different diagrams are used for different type of UML modeling.  There are three important type of UML modeling : 1)Structural modeling:  Structural modeling captures the static features of a system.  They consist of the followings: Class diagrams, Objects diagrams, Deployment diagrams, Component diagram etc  Structural model represents the framework for the system and this framework is the place where all other components exist.  They all represent the elements and the mechanism to assemble them.  E.g. class written once remain same through out the execution. UML Modeling Types

10 2)Behavioral Modeling:  Behavioral model describes the interaction in the system.  It represents the interaction among the structural diagrams.  Behavioral modeling shows the dynamic nature of the system  Activity diagrams, Interaction diagrams, Use case diagrams  Depends upon the behavior of an object/entity object can have more then one state, and depending upon its state its behavior would be different.  E.g. bank account may be working(deposit/ withdraw) Not working(closed/ dead) Cont...

11 3)Dynamic Modeling:  The dynamic model is used to express and model the behavior of the system over time.  It includes support for activity diagrams, state diagrams, sequence diagrams  e.g. user login(id, password), valid tries to login, its set of sequences will be different as compared to an invalid user. Cont...

12 Use-Case Diagram  Use Case Diagram is used to describe the functionalities provided by a system and the users associated with that system.  The Use case diagram is used to identify the primary elements and processes that form the system.  The primary elements are termed as "actors" and the processes are called "use cases."  The Use case diagram shows which actors interact with each use case.

13 Use-Case Diagram  The main purpose of the use-case diagram is:  to help development teams visualize the functional requirements of a system  To help identify relationship of "actors" (human beings who will interact with the system) with essential processes  and understand the relationships among different use cases

14 Elements of a use-case diagram  Use-case diagrams contain the following elements: Actors, which represent users of a system, including human users and other systems. Use Cases, which represent functionality or services provided by a system to users.

15 Actor  Definition:  The outside entity which communicates with the system:  A Person (user)  An external system  Physical Environment  An Actor has a unique name and an optional description  Symbol: UML notation used to represent an actor

16 Actor (Example)  Consider the following scenario related to a “University Management System” :  In a university management system, a Student can submit the assignments, the instructor marks those assignments and then uploads the result. The Student is allowed to view the Results.  Now, by recalling the definition of actor, can you identify the actors in this System?  Student  Instructor

17 Student Instructor Actor (Example/2) Student Instructor Student is an external entity which interacts with the system. Student is a user of this system, as some services are used by it. Instructor is another external entity which interacts with the university management system.

18 Use-case  Represent functionality or services provided by a system to users.  It is a description of set of sequence of actions that a system perform that produces an observable result.  A use case represents a class of functionality provided by the system as an event flow.  Use cases describe the interaction between a primary actor and the system itself

19 Use-case  The use case technique is used in software and systems engineering to capture the functional requirements of a system.  Each use case describes how the actor will interact with the system to achieve a specific goal.  One or more scenarios may be generated from each use case, corresponding to the detail of each possible way of achieving that goal.  Symbol : UML notation used to represent a use- case

20 Use-case (Example)  Consider the same example again:  In a university management system, a Student can submit the assignments, the instructor marks those assignments and then uploads the result. The Student is allowed to view the Results.  Now, by recalling the definition of use-case, can you identify the use-cases in this System?  Submit Assignments  Mark Assignments  Upload Results  View Results

21 Use-case (Example/2)  The use-cases are linked with the functional requirements of this system. In this example :  Student submit the assignments.  Instructor marks the assignments.  Instructor upload the marks.  Student can view the marks.  It is now clear that how actors are interacting with different use-cases of this system.  Now, lets combine actors and use-cases in one diagram?

22 Symbols in Use-Case Diagrams ACTOR USE-CASE INTERACTION: denotes set of messages exchanged among objects NOTES/COMMENTS

23 Use-Case Diagram (University Management System) Student Instructor Submit Assignments Mark Assignments Upload Results View Results SYSTEM BOUNDARY Package: University Management System

24  Other types of associations and relationships;  Generalization between use cases  Generalization between actors  Include relationship between use cases  Extend relationship between use cases Cont...

25  Represented by a line and a hollow arrow  From child to parent  A use case generalization shows that one use case is simply a special kind of another.  A child can be substituted for its parent whenever necessary.  Generalization appears as a line with a triangular arrow head toward the parent use case Generalization between Use cases Child use case Parent use case

26 Example CarMatch Administrator Web Server Register car sharer Transfer car sharer from web server Manually add car sharer Example : ATM

27 Generalization between Actors (examples) student Foreign studentLocal student

28  Some times one use case includes the functionality of another use case.  Include relationship is drawn as an open arrow with dashed lines that points towards the use case that is being included  The word include is written in > Or  If x is a task and y is a sub task but acting as a part of it then use > stereotype  Arrowhead towards the subtask Include relationship between use cases

29 Example

30  There are occasions where one use case may optionally be extended by the functionality in another use case.  The relationship is drawn as an open arrow with dashed line the points towards the use case that is being extended.  The word extend is written in > Or  If x is a task and y is a sub task of x but little bit different  Arrow head towards the main task Extend relationship between use cases

31 Example Passenger Purchase Ticket TimeOut > NoChange > OutOfOrder > Cancel > Turn leftTurn right Take turn > Driver

32 Practice  Read the following case :  Identify the actors  Identify (extract ) the use cases  Construct a proper use-case diagram (with proper symbols & notations)

33 Case-Study  Consider the Library Management System of UOW. A Student is allowed to issue books for a period of two weeks. Student can read newspapers/magazines in the library and can even access the databases for e-books. The Library Staff is responsible for maintaining the records of students and along with the issued books. The Staff marks an entry in the register whenever a student issue or return a book. A fine is charged on a student if he/she fail to return the book on time. The Librarian is there to manage the staff, check the records and prepare reports for DG/DEAN.

34  Gives a graphical representation of domain model.  It represents relationship of classes objects with object specification in detail.  It gives static view of the system  Each class is represented by a rectangle subdivided into three compartments  Name  Attributes  Operations Class diagrams

35 Class Diagram: Visibilities  Modifiers are used to indicate visibility of attributes and operations.  ‘+’ is used to denote Public visibility (everyone)  ‘#’ is used to denote Protected visibility (derived)  ‘-’ is used to denote Private visibility (no one)  By default, attributes are hidden and operations are visible.  The last two compartments may be omitted to simplify the class diagrams

36 An example of Class Account_Name - Custom_Name - Balance +AddFunds( ) +WithDraw( ) +Transfer( ) Name Attributes Operations

37 Other representations of class Boeing 737 length: meter fuelCapacity: Gal doors: int Boeing 737 length: meter fuelCapacity: Gal doors: int lift ( ) roll ( ) thrust ( ) Boeing 737 lift() roll()

38 Class Attributes (Cont’d) Person name : String address : Address birthdate : Date / age : Date ssn : Id Attributes are usually listed in the form: attributeName : Type A derived attribute is one that can be computed from other attributes, but doesn’t actually exist. For example, a Person’s age can be computed from his birth date. A derived attribute is designated by a preceding ‘/’ as in: / age : Date

39 Class Attributes (Cont’d) Person + name : String # address : Address # birthdate : Date / age : Date - ssn : Id Attributes can be: + public # protected - private / derived

40 Class Diagram: Association  Bi-directional association Associations are assumed to be bi-directional  Uni-directional association e.g. Bank Account and person Associations represent relationships between instances of classes. An association is a link connecting two classes. BankAccount Person BankAccount Person

41 Association: Multiplicity and Roles Multiplicity SymbolMeaning 1One and only one 0..1Zero or one M..NFrom M to N (natural language) *From zero to any positive integer 0..*From zero to any positive integer 1..*From one to any positive integer Note: if no multiplicity is given it is assumed to be 1 Association name: represents nature of participants classes in a relationship. Association Role: role played by the participant class Instructor Student 1..* learns fromteaches

42 Notation of Class Diagram: Generalization Generalization expresses a relationship among related classes. It is a class that includes its subclasses. Subtype2 Supertype Subtype1 Student TeachingAssistant Employee Person Student

43 Cont... Vehicle BusTruckCar Boeing 737 BoeingAirplane Boeing 757Boeing 767 Shared target style Separate target style

44 Notation of Class Diagram: Composition Composition: expresses a relationship among instances of related classes. It is a specific kind of Whole-Part relationship. It expresses a relationship where an instance of the Whole-class has the responsibility to create and initialize instances of each Part-class. Composition should also be used to express relationship where instances of the Whole- class have exclusive access to and control of instances of the Part-classes. Class W Class P 1 Class P 2 COMPOSITION Whole Class Part Classes Automobile Engine windows Example

45 Cont... Car 4 WheelLightDoorEngine 4, 102,

46 Notation of Class Diagram: Aggregation Aggregation: expresses a relationship among instances of related classes. It is a specific kind of Container- Containee relationship. It expresses a relationship where an instance of the Container-class has the responsibility to hold and maintain instances of each Containee-class Aggregation is appropriate when Container and Containees have no special access privileges to each other. Class C Class E 1 Class E 2 AGGREGATION Container Class Containee Classes Bag Apples Milk Example

47 Cont... Player class Team 1 * Consists Of

48 Composition Composition is really a strong form of aggregation components have only one owner components cannot exist independent of their owner; both have coincident lifetimes components live or die with their owner e.g. (1)Each car has an engine that can not be share with other car (2) If the polygon is destroyed, so are the points. Aggregations may form "part of" the aggregate, but may not be essential to it. They may also exist independent of the aggregate. Less rigorous than a composition e.g. (1)Apples may exist independent of the bag. (2)An order is made up of several products, but the products are still there even if an order is cancelled. Aggregation vs. Composition

49 Class Diagram example Order -dateReceived -isPrepaid -number :String -price : Money +dispatch() +close() Customer -name -address +creditRating() : String() Corporate Customer -contactName -creditRating -creditLimit +remind() +billForMonth(Integer) Personal Customer -creditCard# OrderLine -quantity: Integer -price: Money -isSatisfied: Boolean Product * 1 1 * Employee * 0..1 * 1 Operations Attributes Name Association Multiplicity: mandatory Multiplicity: Many value Multiplicity: optional Generalization class

50 Interaction Diagrams  In object oriented systems, tasks are performed by objects interacting with other by passing messages.  In UML this interaction is provided by sequence diagrams.  Class diagrams model static nature of system  Interactions diagrams model the dynamic nature of system and emphasis the order of the message over time

51  squares with object type, optionally preceded by object name and colon Cont...

52  These are used to model :  high level interaction between active objects in system  Interaction between objects involved in a use case  Interaction between objects involved in an operation  Generic interactions (showing all possible paths through interaction) Purpose of interaction diagrams

53 Sequence Diagram  Shows how objects communicate with each other over time.  That is, sequence diagrams are used to model object interactions arranged in time sequence and to distribute use case behavior to classes.  They can also be used to illustrate all the paths a particular use case can ultimately produce.  The sequence diagram consists of Active Objects, Messages represented as solid-line arrows, and Time represented as a vertical progression.

54 Sequence Diagram - Objects  A life line illustrates what is happening to an object in a chronological fashion. :Name Life line Activation(focus of control) Object

55 Sequence Diagram – Time & Messages  Messages are used to illustrate communication between different active objects of a sequence diagram. :Name1 :Name2 Message Two Actor Message One

56 Types of Messages  Synchronous (flow interrupt until the message has completed.  1 st object waits until the 2 nd object completes its operations  Asynchronous (don’t wait for response)  1 st object does not wait for the 2 nd object to completes its operations  Flat – no distinction between sysn/async  Return – control flow has returned to the caller.

57 1.Decide the context of the interaction  System, subsystem, use case or operation 2. Identify the structural elements(objects) necessary to carry our functionality of use case 3. Consider alternative scenario that may be required 4. Draw the sequence diagram  Layout the objects from left to right  Starting with the message that starts the interaction  Add focus of control  Add timing constructs Steps in drawing a sequence diagram

58 Sequence Diagram – Compilation :CompilerLinker Actor Compile FileSystem Load Files Save OBJ Files Compile files Link Load OBJ files Link OBJ files Write EXE file

59 Example :making phone call CallerPhoneRecipient Picks up Dial tone Dial Ring notificationRing Picks up Hello

60 Task 1  Draw a sequence diagram for:  In Beauty and the Beast kitchen items came to life. Draw a sequence diagram for making a peanut butter and jelly sandwich if the following objects are alive: knife, peanut butter jar (and peanut butter), jelly jar (and jelly), bread, plate. I may or may not want the crusts cut off. Don’t forget to open and close things like the jars, and put yourself away, cleanup, etc…

61  Draw a sequence diagram showing a customer’s interaction to withdraw money from ATM.  Show all sequence of steps involved e.g. insert card, enter pin number, amount etc. Task 2

62  Purpose of Activity diagrams is listed as under :  Are a means of describing workflows  Can be used as an analysis tool to describe business flows in different level of detail  Describe complex flows within or between use case  At design level, it can be use to describe flow within an operation. Activity diagrams

63  Activity diagram consists of:  Activities  States  transitions Cont...

64  An activity is a unit of work that needs to be carried out  symbol used to represent an activity  Each activity can be followed by another activity (sequencing). Notations Activity name

65  There are four ways in which an activity can be triggered  On Entry: these actions are triggered as soon as the activity starts  Do: these actions take place during the life time of the activity  On Event: these actions take place in response to an event  On Exit: these actions takes place just before the activity completes Triggering an activity

66  Actions -> is triggering of an event Cont... Activity name Entry/ action Do/action Event name/action Exit/action

67  A state in an activity diagram is a point where some event needs to take place before activity continues  Activities & states are roughly equivalent and states can carry out actions just as an activity can.  However activities need to complete all their actions before exiting normally.  States are used to imply waiting, not doing States & Activities Wait for payment

68  There are two special states:  Start State: is the entry point to a flow  Only one start state is allowed in an diagram  Shows as a block dot and is labeled  End State: are drawn as black dots with a surrounding circle Cont...

69  Transition :  Is the movement from one activity to another  The change from one state to another  The movement between states and an activity in either direction.  A transition normally occurs when all the actions of an activity have been completed.  Or when an event triggers the exit from a particular state or activity.  Are shown as arrowed lined between two activity Transition Wait for payment Request payment

70  There are two types of transitions:  Trigger-less transitions : are permissible when exiting activities, and meaning is that the activity has completed all its actions and next phase of workflow can begin  Triggered Transitions: when exiting a state, some event needs to trigger it.  E.g. when waiting for payment, exit from the state could be triggered by a PaymentArrives event Cont... Wait for payment Request payment PaymentArrives

71  There can be more than one transition out of a single activity or a state.  This is used when different events results in a state or activity termination Cont... Wait for payment Chase payment Process payment PaymentPeriodExpires PaymentArrives (amount)

72  A decision points in a workflow where the exit transition from a state or an activity may branch in alternative direction  Depending on a condition  Represented by a diamond. Decision Points

73  Synchronisation bar.  All triggers from this attach to activities that can occur in parallel, with no specific sequence, or concurrently.  Symbol Synchronisation bar or

74 Example Process payment Process Cheque Update cash balance Cheque payment Cash payment Clear Debt

75 Activity Diagrams - Notation  Start at the top black circle If condition 1 is TRUE, go right; if condition 2 is TRUE, go down  At first bar (a synchronization bar), break apart to follow 2 parallel paths  At second bar, come together to proceed only when both parallel activities are done

76 Example

77 Example 2

78 Creating an activity diagram  Modelling a workflow in an activity diagram  Identify a workflow objective.  Decide the pre and post-conditions of the workflow.  Define all activities and states.  Define any objects that are created or modified.  Decide on responsibility for performing the activities.  Connect all elements on the diagram with transitions.  Place decisions on the diagram.  Evaluate your diagram for concurrent workflows.  Set all actions, triggers and guard conditions in the specifications of each model element.

79  Draw an activity diagram to issue book from library Task

80 Possible solution


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