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152 NGUYEN AND DILLON
The quotation alludes to one meaning of “team.” But it is not the only one. In fact, the term
can be used in three different senses:

• In the first sense, a team is a kind of team, for example, Women’s Senior Team. This concept
of “team” turns out to be equivalent to the concept of “competition type.”
• In the second sense, a team is a team of gymnasts in a club, for example, Women’s Senior
Team of the Flippers Club.
• In the third sense, a team is a team from a club that actually participates in a competition,
for example, Women’s Senior Team of the Flippers Club for Town Invitational Meet. This
is the concept of the term “team” explained in the above quotation.

The models in the book seem to confuse these different concepts of “team.”

• In Figures 4–9 (White, 1994, p. 50) and 5–4 (ibid., p. 60), the relationship cardinalities show
that each gymnast can belong to only one team and each team can participate in many competi-
tions. These cardinalities are correct if the term “team” is used in the first or second sense.
• Then, in Figure 6–6 (ibid., p. 71), the relationship cardinalities show that a gymnast can
belong to many teams (correct for “team” in the third sense), and a team can participate in
many competitions (correct for “team” in the first or second sense).
To support the operations of the Gymnastics System, at least two concepts of “team” (the first
and the last) have to be distinctly represented. As the given model stands, it does not capture and
represent the first concept of “team” or “competition type.”
In addition to the problem of identifying classes and relationships, numerous constraints need
to be identified and enforced. For example:

• A judge for an event in a meet must be qualified for that type of event.
• A gymnast participating in a competition as a member of team T must be of a certain age
and gender, and must belong to team T’s club.
• Or, when a gymnast G participates in a competition C, and the competition has event E, then
gymnast G must receive a score for event E of the competition.
Of these three constraints, only the first one is explicitly identified in White (1994). There is
no evidence that any of them is actually enforced (e.g., by reading the collaboration diagrams
and the class specifications).
USING ORM AS A SUPPLEMENTARY TECHNIQUE

Dealing with the Problem of Mutating Concepts

With ORM, when writing down the fact types, we have to specify the “reference schemes” (how
“objects” are identified). In this way, related concepts can be easily distinguished and the problem
of mutating concepts is overcome.
Consider, for example, the “Scoring of a Competition” report in Figure 9.3. In the ORM ap-
proach, we can start by reading a few facts from the report. For example, the fact related to the
score of 41.5 for club Flippers may be expressed as follows: