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160 NGUYEN AND DILLON
Figure 9.5 A Domain Model for the Gymnastics System: The Preferred Model

1
Club Meet
1 1
N N N
N N N 1 N 1 Competition
Gymnast Team Competition
Type
1 1 1
N N N
N N 1 N 1
Member Award Event Event Type
1
N N N
N
1 N
Judge

Now, there remain three binary fact types without a simple key and a quaternary fact type. The
three fact types (EventType is for Gender, Judge is qualified for EventType, Judge is assigned to
Event) are to be represented by three associations. The quaternary fact type can be represented by
class Award (or Score)—though an association class is also a possible choice.
With the choices that we have made, where most concepts are explicitly represented, we arrive
at the class diagram shown in Figure 9.5.

Additional Insight into Possible Class Diagrams

The above simple approach clearly shows the considerable extent to which the fact-based model
can facilitate the construction of the class model. Furthermore, the analysis also leads to an
interesting consequence, that is, we can have an understanding of a range of possible domain
models.
Here is how we arrive at this understanding. First, we note that for the model in Figure
9.5, every important concept is represented explicitly. Now, if we go to the other extreme and
represent the fact type groups for Competition, Event, Team, Member (groups 8–11) implicitly
as associations, we would get the model shown in Figure 9.6. Though strange-looking and
not intuitively appealing, it is still a legitimate domain model in which information about the
application domain is represented as objects (instances of classes) and links (instances of as-
sociations). The two models presented are essentially the two extremes. Other possible models
are those between these two extremes, depending on how we choose to represent certain groups
of fact types.

A COMPARISON ON THEORETICAL GROUNDS

Having covered the practical use of the text analysis and the fact-based approach, we now examine
and contrast their basic premises. The comparison should provide a deeper insight into the differ-
ences between the two approaches.