Page 60 - DCAP308_OBJECT_ORIENTED_ANALYSIS_AND_DESIGN

Object Oriented Analysis and Design

Notes
Figure 5.3: A Derived Attribute

FlightDescription

scheduledDepartTime

scheduledDuration
/scheduledArrivalTime

frequency

startEffectiveDate

stopEffectiveDate

Self Assessment

Fill in the blanks:
8. ...................... is data that can be completely determined from other data.
9. A C++ derived class refers to the subclass of a ......................
10. Derived data that is precomputed must be marked as ...................... or recomputed if
constituent data is changed.

5.4 Packages

You can fit an object model on a single page for many small and medium-sized problems.
However, you will need to organize the presentation of large object models. A person cannot
understand a large object model at a glance. Furthermore, it is difficult to get a sense of perspective
about the relative importance of portions of a large model.

!
Caution You must partition a large model to allow comprehension.
A package is a group of elements (classes, associations, generalizations, and lesser packages)
with a common theme. A package partitions a model, making it easier to understand and
manage. Large applications may require several tiers of packages. Packages form a tree with
increasing abstraction toward the root, which is the application, the top-level package.
As Figure 5.4 shows, the notation for a package is a box with the addition of a tab. The purpose
of the tab is to suggest the enclosed contents, like a tabbed folder.

Figure 5.4: Notation for a Package

Source: http://www.pearsonhighered.com/assets/hip/us/hip_us_pearsonhighered/samplechapter/
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