5.3. Reference Schemes

With uniqueness and mandatory role constraints covered, it is time to consider reference schemes in more depth. With simple identification schemes, each entity is identified by associating it with a single value. For example, a country might be referenced using a code. For instance, Australia may be referenced by the definite description “The Country that has CountryCode ‘AU’”. We usually abbreviate simple reference schemes by parenthesizing the reference mode, or manner in which the value relates to the entity, for example, Country(.code). In practice, more complex reference schemes are often encountered, and we need to deal with them even as early as step 1 of the CSDP, when we verbalize facts.

Before examining these ...

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