UML

1. UML Dr. Zhen Jiang West Chester University E-mail: zjiang@wcupa.edu

2. Outline • Introduction to UML • Objects and Classes • Class Diagrams • Class Icon • Relationships • Constraints

3. UML: Unified Modeling Language • The Unified Modeling Language (UML) is an industry-standard language for specifying, visualizing, constructing, and documenting the artifacts of software systems • The UML definition was led by Grady Booch, Ivar Jacobson, and Jim Rumbaugh (all now at Rational Software)

4. Objects and Classes • What’s object • Identity • State • Behavior • Sequence Diagram • Statechart Diagram • Messages and methods • What’s class • Objects and Classes • Nature of a class • Class Attributes • Operation (Method) • Interfaces • Interfaces and Implementation • Corresponding C++ code

5. Objects • Conceptually, there are many ways to think of an object • something that can be seen or touched • a thing to which some action is directed • something that performs a query action • The structure and behaviour of similar objects are defined in their common class • Objects have thee properties: identity , state, and behaviour (query action)

6. Object Property 1: Identity • Identity is that property of an object which distinguishes it from all other objects • Keep in mind, however, that an object may not have a name; Similarly, an object might have multiple names (aliases) • For this reason, there is a subtle distinction made between the concepts of "name" and "identity"

7. Object Property 2: State • The state of an object encompasses all of the (usually static) properties of the object plus the current (usually dynamic) values of each of these properties

8. Object Property 3: Behaviour • Behaviour is how an object acts and reacts, in terms of its status changes and message/information passing • The state of an object represents the cumulative results of its behaviour

9. Example Objects • There are many physical objects we can examine right in this room • each person is an object • any chair is not an object • each light bulb is an object • Any book is not an object • this room itself is an object (full or not)

10. See if the followings are objects or not: • Desk • Light • Person • Log • The Earth • Clock • Machine • Computer • Saving account • Answer: N, Y, Y, N, Y, Y, Y, Y, Y

11. Objects versus Classes • How would we describe the state, behaviour, and identity for each of these objects • We have looked at objects and we have seen that objects can be "classified" into classes • As programmers, we work with both classes and objects from those classes

12. Classes and Objects • An object is called an "instance" of a class • The terms instance and object are interchangeable • Creating an object from a class is often called instantiation • For example, there are many person objects in this room -- each person is an instance of the person class

13. The Nature of a Class • A class describes the common structure (attributes/state) and behaviour of its instances • For example, • 3.14, 2.71, and 5.5 can be classified as Floats • the following shapes can be classified as Circles

14. In a 2D drawing package, circles have a radius, a line thickness, a line color, and a fill color • Each individual circle (instance) drawn by the user has its own value for each attribute • The programmer writes a Circle class and the program instantiates a Circle object every time the user draws a Circle a snowman made from 9 Circle instances

15. Class Attributes • An attribute is a named property of a class that describes the range of values that instances of the property may hold.(Booch,1999) • An attribute has a type that defines the type of its instances. • Only the object itself should be able to change the value of its attributes. • The values of the attributes define the state of the object

16. Operation (Methods) • An operation is the implementation of a service that can be requested from any object of the class to affect behavior (Booch, 1999) • An operation can be: • Question (does not change the value of the object) • Command (may change the value of the object)

17. Review something Object action action state1 state2 operations/methods attributes: {attribute1, attribute2} structure operation/method attribute1 attribute2 value

18. Light Turn on/off On Off operations/methods: Turn_on/off ( ) attributes: {True, False} structure Turn_on True False Turn_off value

19. Class Diagram • Introduction • Class Icon • Relationships • Constraints

20. Introduction • The class diagram is fundamental to object-oriented programming • UML’s class diagrams capture the attributes and operations of each class as well the relationships that exist between classes

21. Class Icon • Class Icon • Hiding Details • Visibility Notation • Attribute Specification • Operation Specification

22. UML Class Icon • The UML class icon is a rectangle with three compartments: • class name • class attributes • class operations • Attributes are specified in the following form: • object:class name

23. Hiding Detail • You can optionally leave out the attributes, operations, or both in a class icon:

24. UML Member Visibility Notation • UML has three visibility prefixes for members:+ for public, # for protected, and – for private • e.g.

25. Full UML Attribute Specification • The full form of a UML attribute is as follows:[visibility] name [multiplicity] [: type] [= initial value] [{property}] • The property choices are changeable, addOnly, and frozen

26. Full UML Operation Specification • The full form of a UML operation is as follows:[visibility] name [(parameter-list)] [:return-type] [{property}] • The property choices are sequential, concurrent, guarded, and isQuery • The full form of a UML parameter is:[direction] name : type [= default-value] • The direction choices are in, out, and inout

27. UML Class Relationships • A class relationship is a connection between two (or more) classes • The three most important class relationships are generalizations, associations, and aggregations • UML provides a graphical representation for each of the relationships using a different line type for each relationship

28. Class Relationships • Generalization • Association • Association Class • Qualified Association • Ternary Association • Aggregation

29. Generalization • A generalization is a relationship between a general thing (superclass) and a more specific kind of that thing (subclass) • In the UML, generalization requires that objects of the subclass may be used anywhere an object of the superclass appears

30. Association • An association is a structural relationship that specifies that objects of one thing are connected to objects of another

31. Association • Associations can be adorned with a name. Teaching

32. Association • Associations can be adorned with the roles. teacher learner

33. Association • Associations can be adorned with the multiplicity. 1 4..*

34. Association Class (relation attributes) • Each object of association class is one instance of relationship (link) in an association. 1..* 4..*

35. Qualified Association • Qualified association relates two classes and a qualifier. • The qualifier is a special attribute that reduces the effective multiplicity of an association.

36. Ternary Association • A ternary association is a structural relationship that specifies that objects of one thing are connected to objects of other two’s.

37. Aggregation • An aggregation is an association that represents whole/part relationship • The “whole” end of the association relationship is adorned with an open diamond shape (e.g. X is part of Y) • e.g. door:Door is part of car:Car X Y

38. Generalization, Aggregation, and Association • See if the following pairs of classes have generalization, aggregation or association • Faculty & student (as) • Hospital & doctor (as) • Door & Car (ag --<>) • Member & Organization (ag --<>) • People & student (ge <|-- ) • Circle & point (ge --|>) • Department & Faculty (as) • Employee & Faculty (ge <|--) • Item & Printer (ge <|--) • Account & Checking account (ge <|-- )

39. Constraints • Constraints on Object • Constraints on Relations (Ordering) • General Constraints (Dependency)

40. Constraints on Object • The constraints restricts the values that objects can be. • Example: No employee’s salary can exceed the salary of the employee’s boss. {salary <=boss.salary}

41. Constraints on Relations (Ordering) • {Order} indicates that the elements of the “many” end of an association have an explicit order that must be preserved. {ordered} 1 1..*

42. General Constraints (Dependency) • A dependency is a using relationship that states that a change in specification of one thing may affect another thing that uses it (but not necessarily the reverse)

43. General Constraints (Dependency) • Dependencies are often used when one class uses another class as an argument of the operation • Dependencies are also often used to express general constraints. member-of {subset} chair-of

44. (Class Name, attribute, method) vs (Table Name, field, query) • (Class & object) vs (Table & row) • (Table 1, table 2, … ) vs Knowledge relearning with OO techniques to quickly locate the information

45. Design Organize the data into “something” (i.e., object) being queried. Observe the relationship between objects. Describe the queries into methods, changing, updating, and even deleting the attribute information. If necessary, translate class, object, attribute value, and method to table, row, field value, and query.