Chapter 16

1. Chapter 16 UML Class Diagrams CS6359 Fall 2012 John Cole

2. What They Are • They illustrate classes, interfaces, and their associations. They are used for static object modeling. CS6359 Fall 2012 John Cole

3. CS6359 Fall 2012 John Cole

4. Design Class Diagram • A class diagram can be used to visualize a domain model. We also need a unique term to clarify when the class diagram is used in a software or design perspective. A common modeling term for this purpose is design class diagram (DCD) CS6359 Fall 2012 John Cole

5. Design Class Diagram CS6359 Fall 2012 John Cole

6. Classifier • A UML classifier is “a model element that describes behavioral and structure features”. Classifiers can also be specialized. They are a generalization of many of the elements of the UML, including classes, interfaces, use cases, and actors. In class diagrams, the two most common classifiers are regular classes and interfaces. CS6359 Fall 2012 John Cole

7. Showing UML Attributes • Attribute text notation such as: currentSale : Sale, Association line notation, or both • <visibility> name : type multiplicity = default {property string} • Attributes are assumed private if no visibility is given • Arrow shows that the object where the arrow starts has one object of the object to which it points. CS6359 Fall 2012 John Cole

8. UML Attributes CS6359 Fall 2012 John Cole

9. UML Attributes • Multiplicity shows how many on the left can associate with how many on the right • Role name • Attributes are assumed private unless otherwise noted CS6359 Fall 2012 John Cole

10. Attribute Text vs. Association Lines • Use text notation for primitive data types, even things like Zip codes that may have components but are not complex • Use association for everything else. CS6359 Fall 2012 John Cole

11. Collection Attributes CS6359 Fall 2012 John Cole

12. Note Symbols • A UML note symbol is displayed as a dog-eared rectangle with a dashed line to the annotated element; they’ve already been used throughout the book. A note symbol may represent several things, such as: • a UML note or comment, which by definition have no semantic impact • a UML constraint, in which case it must be encased in braces ‘{…}’ • a method body—the implementation of a UML operation CS6359 Fall 2012 John Cole

13. Operations and Methods • A method is the implementation of an operation CS6359 Fall 2012 John Cole

14. The Create operation • This is a constructor call • You can use <<constructor>> to make this explicit CS6359 Fall 2012 John Cole

15. Keywords • A UML keyword is a textual adornment to categorize a model element • Keywords include <<actor>>, <<Interface>>, [abstract], [ordered] CS6359 Fall 2012 John Cole

16. Stereotypes, Profiles, Tags • Stereotypes are also shown in guillemets symbols . They are not keywords. A stereotype represents a refinement to an existing modeling concept CS6359 Fall 2012 John Cole

17. Properties and Property Strings • A property is “a named value denoting a characteristic of an element • Textual approach is to use the UML property string{name1=value1, name2=value2} format, such as {abstract, visibility=public} CS6359 Fall 2012 John Cole

18. Generalization • A taxonomic relationship between a more general classifier and a more specific classifier • This can imply inheritance, but not at the conceptual level. CS6359 Fall 2012 John Cole

19. Dependency • Similar to association. Indicates that a client element has knowledge of another supplier element, and a change in the supplier could affect the client • (Supplier and client are descriptive terms, not classes) • Dependency lines are common on class and package diagrams • Use to depict global, parameter variable, local variable, and static-method dependency CS6359 Fall 2012 John Cole

20. Types of Dependency • Having an attribute of supplier type • Send a message to a supplier • Receiving a parameter of supplier type • Supplier is a superclass or interface • Indicated by a dashed line arrow CS6359 Fall 2012 John Cole

21. Interfaces CS6359 Fall 2012 John Cole

22. Composition Vs. Aggregation • Aggregation is a vague association suggesting whole-part relationships. No meaningful semantics in UML versus association. • Composition, or composite aggregation, is a strong kind of whole-part relationship. • Implies that an instance of the part belongs to only one composite instance of the whole CS6359 Fall 2012 John Cole

23. Composition • For example the Monopoly board consists of 40 squares • A square can be part of only one board at any time. CS6359 Fall 2012 John Cole

24. Constraints • Constraints is a restriction on a UML element. • Shown as text between braces • {size > 0} CS6359 Fall 2012 John Cole

25. Qualified Association • Uses a qualifier to select an object or set of objects from a larger set • For example, looking up something in a HashMap CS6359 Fall 2012 John Cole

26. Association Class • Allows you to treat an association as a class, such that it can have attributes CS6359 Fall 2012 John Cole

27. Singleton Class • Only one instance of a Singleton class (pattern explained later) is ever instantiated. • For example, your main class in most programs is a Singleton, although this may not be its dominant pattern. CS6359 Fall 2012 John Cole

28. Template Classes and Interfaces • These are equivalent to C++ or Java “generics.” • That is, you can type a collection class. CS6359 Fall 2012 John Cole

29. User-Defined Compartments • In a class diagram you can define your own compartments: CS6359 Fall 2012 John Cole

30. Active Class • An active object runs on and controls its own thread of execution • In UML, it is shown with double vertical lines on the left and right of the class box. CS6359 Fall 2012 John Cole