Page 49 - DCAP308_OBJECT_ORIENTED_ANALYSIS_AND_DESIGN

Unit 4: Advanced Class Modelling – I

Do not confuse an enumeration domain with generalization. You should introduce generalization Notes
only when at least one subclass has significant attributes, operations, or associations that do not
apply to the superclass. Do not introduce a generalization just because you have found an
enumeration domain.

Notes You can define a domain intensionally (by formula), extensionally (by explicitly
listing occurrences), or in terms of another domain.

Task Make distinction between enumeration domain and structured domain.

Self Assessment

Fill in the blanks:
1. ........................ is the relationship between an object and its class.

2. A ....................... is an operation on a class rather than on instances of the class.
3. Attribute ....................... specifies the possible number of values for an attribute and is
listed in brackets after the attribute name.

4. The collection of ....................... in a candidate key must be minimal.
5. An ....................... domain is a domain that has a finite set of values.

4.2 Association Ends

An association end is an endpoint of the line drawn for an association, and it connects the
association to a class. An association end may include any of the following items to express
more detail about how the class relates to the other class or classes in the association:

Rolename
Multiplicity specification
Aggregation
Qualifier

4.2.1 Rolename

A rolename is optional and indicates the role a class plays relative to the other classes in an
association, how the other classes “see” the class or what “face” the class projects to the other
classes in the relationship. A rolename is shown near the end of an association attached to a class.

Example: A work product is seen as input by a unit of work where the unit of work is
seen as a consumer by the work product; a work product is seen as output by a unit of work
where the unit of work is seen as a producer by the work product, as shown in Figure 4.8.

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