Design Patterns Explained

46 Part II • The Limitations of Traditional Object -Oriented Design
Terminology:
classifying the shapes
cut from the sheet
metal
Figure 3-1 Example of a piece of sheet metal.
What are expert systems?
An expert system is a special computer system that uses the rules of a
human expert(s) to make automated decisions. Building expert
systems involves two steps. First, acquire and model the set of
rules that experts use to make decisions and accomplish the task.
Second, implement this set of rules in the computer system; this
step usually uses some sort of commercially available expert system
tool. The first step is by far the more difficult assignment for
the analyst.
Understand the Vocabulary
The first task in analysis is to understand the vocabulary used by
the users and the experts in the problem domain. The most impor tant
terms used are those that describe the dimensions and geome try in
the sheet metal.
As shown in Figure 3-1, a piece of sheet metal is cut to a particular
size and has shapes cut out inside it. Experts call these cutouts by
the general name "feature." A piece of sheet metal can be fully
specified by its external dimensions and the features contained in it.