Documenting the decision logic

After you document the information in the sub-decisions, start documenting the decision logic using decision tables.

Decision tables are organized by rows and columns, where each row is a decision rule and each decision rule consists of considerations and a conclusion.

decision rule
A rule that consists of one or more considerations and a single conclusion.
consideration
A condition that, when it is tested, evaluates to either true or false. Considerations in a decision table map to the decision inputs that are defined for a given decision or sub-decision in the decision diagram. The map might consist of complex expression that involves more than one decision input.
conclusion
A value that is assigned to the decision output when all the conditions in the decision rule are met or are evaluated to true. The conclusion maps directly to the decision output that is defined for a given decision or sub-decision in the decision diagram.

To document the decision logic, in the decision diagram right-click a sub-decision and click Details. In the window, switch to the Decision tab.

Under Decision Table, click Create table using inputs & output or Create blank table depending on how you want to document the decision logic.

For example, the following figure shows the decision logic for the Validate Offer Compliance decision, which determines whether the salary proposed for offer to a potential new hire complies with the corporate salary guidelines.
The figure illustrates that each decision rule consists of three considerations and a conclusion. The considerations are position, department, and proposed salary. The conclusion is that the proposed salary for the offer is compliant. If the proposed salary to a new hire in a certain position of a specific department is within the proposed salary scope, the proposed salary for the offer complies with the corporate salary guidelines. For example, for the position of VP in the Sales department, the proposed salary is more than $180,000 and less than $250,000. The conclusion is that the proposed salary is compliant in this range.
Tips for building decision tables:
  • Limit the number of consideration columns so that the table is easier to read. If you have more than seven or eight consideration columns, consider breaking the decision into sub-decisions.
  • Make each decision rule unique, meaning that no more than one decision rule can evaluate to true for any given set of inputs and there is no overlap between rules.
  • Do not imply the order of evaluation in a decision table.
  • Ensure that a decision table is as complete as possible.
You can also add exceptions for the decision logic so that the decision table is not cluttered with many decision rules that have the same meaning. An exception table for a decision table provides an else or otherwise clause. To add an exception, click Add Exceptions and edit the exception table. The following figure shows an example of how you might document a decision table with an exception table.
The figure shows that if the proposed salary to a new hire in a certain position of a specific department is not within the proposed salary scope, the proposed salary for the offer does not comply with the corporate salary guidelines.