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CS 426Senior Projects

Chapter 9: RelationshipsChapter 10: Inheritance and

Polymorphism[Arlow and Neustadt, 2005]

February 12, 2009

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OutlineRelationships:

LinksAssociationsDependencies

Inheritance and Polymorphism:GeneralizationClass inheritancePolymorphismAdvanced generalization

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Relationships: Links & Associations

Relationships = semantic connections between modeling elements

Links = connections between objects

Associations = connections between classes

Links are instances of associations

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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

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.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.

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..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]

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Associations: Semantics

Associations are relationships between classes

Links depend on associations, and instantiate them Fig. 9.5 [Arlow & Neustadt 2002]

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Associations: Syntax

The syntax for an association includes: Association name Role names Multiplicity Navigability

Example of association, Fig. 9.6 [Arlow & Neustadt 2005]

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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]

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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]

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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]

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Associations: Hierarchies & Networks

Example of association hierarchy, Fig. 9.11 [Arlow and Neustadt 2005]

Example of association network, Fig. 9.12 [Arlow and Neustadt 2005]

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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]

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Associations: Modeled using Attributes

One-to-one and one-to-many associations can be modeled using attributes

Fig. 9.16 [Arlow & Neustadt 2005]

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Associations: Association Classes.

Many-to-many associations can lead to association classesExample of many-to-many association, Fig. 9.18 [Arlow & Neustadt 2005]

Corresponding association class, Fig. 9.19 [Arlow & Neustadt 2005]

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Associations: .Association Classes

However, many-to-many associations can also be modeled using regular classes, e.g., Fig. 9.20 [Arlow & Neustadt 2005]

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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 dependencyTable 9.2[Arlow & Neustadt2005]

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Dependencies: .Definition and Types

Examples of different types of dependenciesFig. 9.23 [Arlow and Neustadt 2005]

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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 theabove example

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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]

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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>>)

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Generalization Generalization applies to all classifiers and

to some other elements such as associations, states, and events

Example of generalization, Fig. 10.2 [Arlow & Neustadt 2005]

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Inheritance: Overriding.

Example of class hierarchy, Fig. 10.3 [Arlow & Neustadt 2005]

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Inheritance: .Overriding

Example of overriding, Fig. 10.4 [Arlow & Neustadt 2005]

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Inheritance: Abstract Classes & Operations

Example of abstract classes and operations, Fig. 10.5 [Arlow & Neustadt 2005]

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Inheritance: Level of Abstraction

In generalization hierarchies it is important to maintain a uniform level of abstraction at each level

Incorrect example, Fig. 10.6 [Arlow & Neustadt 2005]

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Polymorphism… Polymorphism means “many forms”. A polymorphic

operation has several different implementations Example of polymorphism, Fig. 10.7 [Arlow & Neustadt,

2002]

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.Polymorphism..

Example of polymorphism “in action,” Fig. 10.8 [Arlow & Neustadt 2005]

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..Polymorphism.

Object diagram with polymorphism, Fig. 10.9 [Arlow & Neustadt 2005]

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…Polymorphism Another example of polymorphism, Fig. 10.10 [Arlow

& Neustadt 2005]

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Advanced generalization: generalization sets.

An example of generalization set, Figs. 10.11 & 10.12 [Arlow & Neustadt 2005]

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Advanced generalization: .generalization sets

Constraints on generalization sets Table 10.1 and Fig. 10.14 [Arlow & Neustadt 2005]

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Advanced generalization: powertypes

Simple example of powertypes, Fig. 10.15 [Arlow & Neustadt 2005]