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This chapter discusses typical design considerations when designing and implementing a decision with a limited number of possible outcomes using Blueriq.

When modeling a decision that is limited to two values (for instance Boolean), there are several ways to achieve this:

Using a default value expression
Using a constant value and a business rule
Using two business rules
Using a decision table

Default value expression

Blueriq Knowledge Base > Setting a business value > image-2024-1-3_11-45-48.png

Constant value combined with business rule

Blueriq Knowledge Base > Setting a business value > image-2024-1-3_11-46-21.png

Blueriq Knowledge Base > Setting a business value > image-2024-1-3_11-46-53.png

Two business rules

Blueriq Knowledge Base > Setting a business value > image-2024-1-3_11-47-44.png

Blueriq Knowledge Base > Setting a business value > image-2024-1-3_11-48-0.png

Decision table

Blueriq Knowledge Base > Setting a business value > image-2024-1-3_11-49-18.png

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

It is perhaps even more tempting to skip the [ ]-column for ELSE, but it is also 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 redundant.

What to use?

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

Whenever the result depends on multiple input values, it is best to use a decision table.
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.
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, regardless of the outcome.
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.

Main chapter: Design considerations

Next: Designing decision tables