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There are several ways to organize those constants in a business model.They will be discussed below.

Entity

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with constants

One way of organizing constant values is combining them in a singleton entity. Of course the attributes of this entity do not share any commonality, except for the fact that they are constants. Business engineers that uphold strict rules of elegant modeling might frown upon such an entity, whereas the more pragmatic business engineers favor one particular space in the business model where all constants are stored and managed.

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Attributes, set by a single decision table

Another way of organizing constant values is setting them in one single decision table, while the constants themselves are declared wherever the business engineer thinks they belong. This scenario can also be used when using a one entity to store all constants together. The default value of these constants is left out, but one (or perhaps even more) decision table sets the values.

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One might argue in favor of using any of the three scenarios discussed here. Other scenarios may be possible as well. There is one con that the three scenarios mentioned here have in common: It is not possible to add a justification for each constant. After all, default values do not have justifications, neither do reusable expressions. Decision tables can have a justification, but only for the complete set of derived attributes. If justification per constant is necessary, a decision table for each constant is the only option.

None

Another possible scenario is to not gather constants at all and just make use of the values that are affiliated with these constants. See the example below where the maximum amount of savings is not declared as a constant. The value 27500 is merely used in a decision table to determine if an applicant does not have too much savings.

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Of course the decision shown above could also have been modeled using a constant default value combined with a business rule or a default value expression, as shown below.

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Using a default expression:

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