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  1. Using a default value expression
  2. Using a constant value and a business rule
  3. Using two business rules
  4. Using a decision table

Default value expression

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Constant value combined with business rule

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Two business rules

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Decision table

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It is tempting to skip the column for male Male, but it is strongly advised to model a comprehensible table. In most cases, comprehensibility implies completeness (the mere fact that "male" Male is missing from a gender-table might cause suspicion).

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It is perhaps even more tempting to skip the [ ]-column for ELSE, but it is also strongly advised to model an ELSE-column whenever the values are not restricted by a value list.

If Applicant.Gender was in fact limited by a value list consisting of the values Male and Female and it is obvious the set will never expend, the ELSE-column would have been otioseredundant.

What to use?

The choice of method is often based on the preference of the business engineer. General recommendations are listed below:

  1. Whenever the result depends on multiple input values, it is best to use a decision table.
  2. Whenever the result is a calculation, it is probably best to use an attribute displayed on a form with a business rule or default expression.
  3. When using justifications (and you will most likely use them, since they are a best practice), the default value expression has limits; only one justification can be used, whether regardless of the outcome is true or false.
  4. It is recommended to formally decide which method to use and capture that in an architecture document. A consistent use of a style throughout a project will help the maintainability of a project. There are many roads that lead to Rome, but within one project it is best if all business engineers follow the same road.

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 Main chapter: Design considerations

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Next: Designing decision tables