Schaum's Outline Series

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CHAPTER 11 Object-Oriented Development
sometimes have special attributes. This is usually an effective approach to finding
inheritance.
The opposite approach is also sometimes useful. It is a bottom-up approach,
which is to group all similar items and look for the commonality. The intersection
of all the similar items will become the base class.
EXAMPLE 11.6
Identifythe possible inheritance in the grocerystore (Example 11.4).
A top-down approach would help to realize that the meat department and the
produce department have special processing of the items. This would lead to a
base class of items and derived classes of meat and produce. An expert in the
domain of grocerystores could help to identifyall the other derived classes that
can occur in a grocerystore.
Additionally, a bottom-up approach would find the commonality among the
objects losses, discount, return, and purchase. This suggests that those
objects can be derived from an object transaction. See Fig. 11-5.
suppliers
shipment
item
quantity
produce meat
grocery
store
name
address
inventory
11.2.3 IDENTIFYING REUSE
transaction
customer
losses discount return purchase
Fig. 11-5
Reuse is one of the promises of object-oriented software. However, reuse rarely
happens by itself. The first step in identifying reuse is a task called domain analysis.
Domain analysis is the process of reviewing the problem domain to determining
what objects and functions are common to all activities. Without good domain
knowledge, it will be hard to identify what commonalities exist between all similar
systems in that domain. For reuse to be effective, the parts that will be useful in
multiple solutions in that domain must be identified. This means understanding
the potential commonalities.
Approaches to reuse can be top-down or bottom-up. Bottom-up approaches
look for low- or middle-level classes that will be common in most solutions in that