Understanding completeness, consistency and the SAP Signavio Verification Feature

One of the typical problems in creating decision tables are missing rules. In the example, no rule is defined for the Business type of customer, this means that there is a rule missing. No rule can fire when the type of customer is a Business customer. As a result, the decision table is incomplete.

Incomplete decision tables are a problem for unique hit policies. Because when the unique hit policy is used, there should be exactly one rule that fires for every possible combination of input values. It is crucial that the decision table is complete.

Manually controlling for completeness of the decision table is challenging to overcome, so SAP Signavio offers an automatic verification feature for decision tables. Click on the verify button in the upper right corner of the decision table dialog.

When the verify button is clicked, the SAP Signavio Process Manager will automatically check the table for completeness. When there are errors detected, a box appears which advises the missing rules. In this case, there is no rule defined for (!Private, any). This means that there is no rule for the Business customer.

The verify function advised us that the rule for Business customer was missing, so we added it to the table. Now the decision table is complete because there is a rule for all possible input value combinations.

An inconsistent decision table has overlapping rules with different output values. With the unique hit policy, only one rule is allowed to fire, so overlapping rules are not allowed. The SAP Signavio verification feature will detect errors that don't comply with the consistency requisite.

In the above example, rule one overlaps with rule two, three and four. This breaches the consistency requisite for the unique hit policy.