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UML Class Diagrams and Packages

UML Class Diagrams and Packages. Dr. Hoang Huu Hanh, OST – Hue University hanh-at-hueuni.edu.vn. Agenda. What is a Class Diagram? Essential Elements of a UML Class Diagram Packages and Class Diagrams Analysis Classes Approach Tips Object and Class Constructing. What is a Class Diagram?.

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UML Class Diagrams and Packages

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  1. UML Class Diagrams and Packages Dr. Hoang Huu Hanh, OST – Hue University hanh-at-hueuni.edu.vn

  2. Agenda • What is a Class Diagram? • Essential Elements of a UML Class Diagram • Packages and Class Diagrams • Analysis Classes Approach • Tips • Object and Class Constructing UML Class Diagrams

  3. What is a Class Diagram? • A class diagram describes the types of objects in the system and the various kinds of static relationships that exist among them • A graphical representation of a static view on static elements • A central modeling technique that is based on object-oriented principles • The richest notation in UML UML Class Diagrams

  4. Essential Elements • Class • Attributes • Operations • Relationships • Associations • Generalization • Dependency • Realization • Constraint Rules and Notes UML Class Diagrams

  5. Window size: Sizevisibility: boolean display()hide() Classes • A class is the description of a set of objects having similar attributes, operations, relationships and behavior. Class Name Attributes Operations UML Class Diagrams

  6. Employee Department Company Associations • A semantic relationship between two or more classes that specifies connections among their instances. • A structural relationship, specifying that objects of one class are connected to objects of a second (possibly the same) class. • Example: “An Employee works in a department of a Company” UML Class Diagrams

  7. Associations (cont.) • An association between two classes indicates that objects at one end of an association “recognize” objects at the other end and may send messages to them. • This property will help us discover less trivial associations using interaction diagrams. UML Class Diagrams

  8. Associations (cont.) Role name Association name instructor StaffMember Student 1..* instructs * Role Navigable (uni-directional) association Multiplicity * pre - requisites Courses 0..3 Reflexive association UML Class Diagrams

  9. Associations (cont.) • To clarify its meaning, an association may be named. • The name is represented as a label placed midway along the association line. • Usually a verb or a verb phrase. • A role is an end of an association where it connects to a class. • May be named to indicate the role played by the class attached to the end of the association path. • Usually a noun or noun phrase • Mandatory for reflexive associations UML Class Diagrams

  10. Associations (cont.) • Multiplicity • The number of instances of the class, next to which the multiplicity expression appears, that are referenced by a single instance of the class that is at the other end of the association path. • Indicates whether or not an association is mandatory. • Provides a lower and upper bound on the number of instances. UML Class Diagrams

  11. Associations (cont.) • Multiplicity Indicators UML Class Diagrams

  12. 2..* 1..* Door Car House Aggregation • A special form of association that models a whole-part relationship between an aggregate (the whole) and its parts. • Models a “is a part-part of” relationship. Whole Part UML Class Diagrams

  13. Aggregation (cont’d) • Aggregation tests: • Is the phrase “part of” used to describe the relationship? • A door is “part of” a car • Are some operations on the whole automatically applied to its parts? • Move the car, move the door. • Are some attribute values propagated from the whole to all or some of its parts? • The car is blue, therefore the door is blue. • Is there an intrinsic asymmetry to the relationship where one class is subordinate to the other? • A door is part of a car. A car is not part of a door. UML Class Diagrams

  14. 1 Circle Point Circle Point 3..* Polygon Composition • A strong form of aggregation • The whole is the sole owner of its part. • The part object may belong to only one whole • Multiplicity on the whole side must be zero or one. • The life time of the part is dependent upon the whole. • The composite must manage the creation and destruction of its parts. UML Class Diagrams

  15. An abstract class Shape{abstract} Super Class Generalization relationship Sub Class Circle Generalization • Indicates that objects of the specialized class (subclass) are substitutable for objects of the generalized class (super-class). • “is kind of” relationship. {abstract} is a tagged value that indicates that the class is abstract. The name of an abstract class should be italicized UML Class Diagrams

  16. Generalization • A sub-class inherits from its super-class • Attributes • Operations • Relationships • A sub-class may • Add attributes and operations • Add relationships • Refine (override) inherited operations • A generalization relationship may not be used to model interface implementation. UML Class Diagrams

  17. Dependency • A dependency indicates a semantic relation between two classes although there is no explicit association between them. • A stereotype may be used to denote the type of the dependency. Iterator <<friend>> Vector UML Class Diagrams

  18. Realization • A realization relationship indicates that one class implements a behavior specified by some interface • An interface can be realized by many classes • A class may realize many interfaces LinkedList <<interface>>List LinkedList List UML Class Diagrams

  19. id: long { value > 0 } Customer 1 * Order may be canceled { total < $50 } Constraint Rules and Notes • Constraints and notes annotate among other things associations, attributes, operations and classes. • Constraints are semantic restrictions noted as Boolean expressions. Constraint Note UML Class Diagrams

  20. TrafficReport Offender 1 issues * TrafficPoliceman 1..* 1 id : long name : String description : String id : long occuredAt : Date reports of 1..* Policeman Violation id : long name : String id : long rank : int description : String <<abstract>> TVRS Example UML Class Diagrams

  21. Name UML Packages • A package is a general purpose grouping mechanism. • Commonly used for specifying the logical architecture of the system. • A package does not necessarily translate into a physical sub-system. UML Class Diagrams

  22. UML Packages (cont’d) • Emphasize the logical structure of the system (High level view) • Higher level of abstraction over classes. • Aids in administration and coordination of the development process. UML Class Diagrams

  23. A D E F G C B Packages and Class Diagrams • Add package information to class diagrams UML Class Diagrams

  24. a.A b.b.D b.b.E b.a.F b.a.G a.C a.B Packages and Class Diagrams • Add package information to class diagrams b a b.a b.b UML Class Diagrams

  25. Analysis Classes • A technique for finding analysis classes which uses three different perspectives of the system: • The boundary between the system and its actors • The information the system uses • The control logic of the system UML Class Diagrams

  26. Boundary Classes • Models the interaction between the system’s surroundings and its inner workings • User interface classes • Concentrate on what information is presented • Don’t concentrate on visual asspects • Example: ReportDetailsForm • System / Device interface classes • Concentrate on what protocols must be defined. • Don’t concentrate on how the protocols are implemented UML Class Diagrams

  27. Entity Classes • Models the key concepts of the system • Usually models information that is persistent • Can be used in multiple behaviors • Example: Violation, Report, Offender. UML Class Diagrams

  28. Control Classes • Controls and coordinates the behavior of the system • Delegates the work to other classes • Control classes decouple boundary and entity classes • Example: • EditReportController • AddViolationController UML Class Diagrams

  29. TVRS Example UML Class Diagrams

  30. Object and Class Constructing

  31. Objectives • Provide guidelines on how to determine the classes/objects in the system • Define class/object structuring criteria

  32. Categorization of Application Classes

  33. External Classes and Interface Classes • External classes are classes that are external to the system and that interface to the system. • Interface (boundary) classes are classes internal to the system that interface to the external classes.

  34. Categorization of External Classes

  35. Identifying Interface Classes • Each of the external classes interfaces to an interface class in the system. • An external user class interfaces to a user interface class • An external system class interfaces to a system interface class • An external input device class interfaces to an input device interface class • An external output device class interfaces to an output device interface class • An external I/O device class interfaces to an I/O device interface class • An external timer class interfaces to an internal timer class

  36. Banking System: External Classes and Interface Classes

  37. Entity Classes • Store information • Often mapped to relational database during design

  38. Control Classes • A control class provides the overall coordination for execution of a use case. • Makes overall decision • Control objects decides when, and in what order, other objects participate in use case • Interface objects • Entity objects • Simple use cases do not need control objects.

  39. Kinds of Control Classes • Coordinator class • Provides sequencing for use case • Is not state dependent • State dependent control class • Defined by finite state machine • Timer class • Activated periodically

  40. Example: Coordinator Object

  41. Example: State Dependent Control Object

  42. Example: Timer Object

  43. Application Logic Classes • Business logic class • Defines business-specific application logic (rules) for processing a client request • Usually accesses more that one entity object • Algorithm class • Encapsulates algorithm used in problem domain • More usual in scientific, engineering, real-time domains

  44. Example: Business Logic Object

  45. Example: Algorithm Object

  46. Tips • Don’t try to use all the various notations. • Don’t draw models for everything, concentrate on the key areas. • Draw implementation models only when illustrating a particular implementation technique. UML Class Diagrams

  47. Note: Unifying Concepts • classifier-instance dichotomy • e.g. an object is an instance of a class ORa class is the classifier of an object • specification-realization dichotomy • e.g. an interface is a specification of a class ORa class is a realization of an interface • analysis-time vs. design-time vs. run-time • modeling phases (“process creep”) • usage guidelines suggested, not enforced Behavioral Modeling with UML

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