1. CS 426 Senior Projects Chapter 9: Relationships
Chapter 10: Inheritance and Polymorphism
[Arlow and Neustadt, 2005]
February 21, 2012

2. Outline Relationships: Inheritance and Polymorphism: Links
Associations
Dependencies
Inheritance and Polymorphism:
Generalization
Class inheritance
Polymorphism
Advanced generalization

3. Relationships: Links & Associations
Relationships = semantic connections between modeling elements
Links = connections between objects
Associations = connections between classes
Links are instances of associations

4. Links..
A link is a connection between objects that communicate via messages
Links can be:
Unidirectional, if only one object (the source) contains a reference to the other (the target). Navigability is shown by an arrowhead at the target end of the link.
Bidirectional, if both objects have a reference to the other. Bidirectional links are shown using unadorned lines with no arrowheads.
Object diagrams show objects and their relationships at some point in time.
Thus, links are dynamic connections between objects

5. .Links. Example of object diagram, Fig. 9.2 [Arlow & Neustadt 2002].
It shows objects, links, and roles. It also illustrates the “oblique” style of drawing paths in UML diagrams.

6. ..Links Example of unidirectional link, Fig. 9.3 [Arlow &
Neustadt 2005]
The “orthogonal”
style of drawing paths
in UML diagrams, Fig.
9.4 [Arlow & Neustadt
2002]

7. Associations: Semantics
Associations are relationships between classes
Links depend on associations, and instantiate them Fig. 9.5 [Arlow & Neustadt 2002]

8. Associations: Syntax The syntax for an association includes:
Association name
Role names
Multiplicity
Navigability
Example of association, Fig. 9.6 [Arlow & Neustadt 2005]

9. Associations: Multiplicity..
Multiplicity constrains the number of objects of a class that can be involved in a given relationship at any point in time
Fig. 9.8 [Arlow & Neustadt 2005]

10. Associations: .Multiplicity.
There is no default value for multiplicity in UML. If not specified, multiplicity is undecided
Examples of multiplicity syntax, Table 9.1 [Arlow & Neustadt 2005]

11. Associations: ..Multiplicity
Multiplicity constraints encode business rules of the model
It is important to “read the model as written”
Figure 9.9 [Arlow & Neustadt 2005]

12. Associations: Hierarchies & Networks
Example of association
hierarchy, Fig. 9.11
[Arlow and Neustadt 2005]
network, Fig. 9.12

13. Associations: Navigability
Navigability can be read “messages can only be sent in the direction of the arrow”
Relationships without arrows are bidirectional
Unidirectional associations reduce coupling between classes
Fig. 9.13
[Arlow & Neustadt 2005]

14. Associations: Modeled using Attributes
One-to-one and one-to-many associations can be modeled using attributes
Fig [Arlow & Neustadt 2005]

15. Associations: Association Classes.
Many-to-many associations can lead to association classes
Example of many-to-many association, Fig [Arlow & Neustadt 2005]
Corresponding association class, Fig [Arlow & Neustadt 2005]

16. Associations: .Association Classes
However, many-to-many associations can also be modeled using regular classes, e.g., Fig [Arlow & Neustadt 2005]

17. Dependencies: Definition and Types.
“A dependency is a relationship between two elements where a change to one element (the supplier) may affect or supply information needed by the other element (the client)” [Rumbaugh et al., The UML Reference Manual]
Three types of
dependency
Table 9.2
[Arlow & Neustadt
2005]

18. Dependencies: .Definition and Types
Examples of different types of dependencies
Fig [Arlow and Neustadt 2005]

19. Dependencies: Usage dependencies
The <<use>> dependencies are the most common type of dependency. They state that the client makes use of the supplier in some way.
Example, Fig. 9.24
[Arlow & Neustadt 2005]
Java code for the
above example

20. Dependencies: Abstraction dependencies
Abstraction dependencies are dependencies between model elements that are at different level of abstraction: <<trace>>, <<substitute>>, <<refine>> and <<derive>> Examples for <<derive>> Table 9.3 [Arlow & Neustadt 2005]

21. Dependencies: Permission dependencies
Permission dependencies indicate the capability of one model element to access another model element.
Examples of permission dependencies:
<<access>>
<<import>>
<<permit>> (formerly <<friend>>)

22. Generalization
Generalization applies to all classifiers and to some other elements such as associations, states, and events
Example of generalization, Fig [Arlow & Neustadt 2005]

23. Inheritance: Overriding.
Example of class hierarchy, Fig [Arlow & Neustadt 2005]

24. Inheritance: .Overriding
Example of overriding, Fig [Arlow & Neustadt 2005]

25. Inheritance: Abstract Classes & Operations
Example of abstract classes and operations, Fig [Arlow & Neustadt 2005]

26. Inheritance: Level of Abstraction
In generalization hierarchies it is important to maintain a uniform level of abstraction at each level
Incorrect example, Fig [Arlow & Neustadt 2005]

27. Polymorphism…
Polymorphism means “many forms”. A polymorphic operation has several different implementations
Example of polymorphism, Fig [Arlow & Neustadt, 2002]

28. .Polymorphism..
Example of polymorphism “in action,” Fig [Arlow & Neustadt 2005]

29. ..Polymorphism.
Object diagram with polymorphism, Fig [Arlow & Neustadt 2005]

30. …Polymorphism
Another example of polymorphism, Fig [Arlow & Neustadt 2005]

31. Advanced generalization: generalization sets.
An example of generalization set, Figs & [Arlow & Neustadt 2005]

32. Advanced generalization: .generalization sets
Constraints on generalization sets Table 10.1 and Fig [Arlow & Neustadt 2005]