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Relationships relate concepts
across a taxonomy of concepts. For example, the relationship hasActivity related
the class Organization with the class Activity. This means that an organization in
the tourism industry may supply a kind of activity to its customer, such as Hiking
and Surfing.
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While classes describe concepts in the domain, specific elements of a class are
instances. For example, a class of WeatherConditon represents all the weather
Develop ng Dynam c Packag ng Appl cat ons
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conditions that can be verified. Specific weather conditions are instances of this
class, such as Cloudy, Showers, and Scattered Showers. However, deciding whether
something is a concept of an instance is difficult and often depends on the application
(Brachman, McGuinness, Patel-Schneider, Resnick, & Borgida, 1991).


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