Decision table is one of the tools that helps. It provides a systematic approach in mining and uncovering business logic. In a decision table, business logic is partitioned into the following parts.
Case Study - Supermarket Delivery Service
V&P is the largest supermarket chain in the city. As the city's foremost supermarket, V&P is dedicated to provide its customers with quality products and services. Recently, V&P has decided to review their delivery service to achieve the followings:
- Standardize the services of all branches to provide customers with a unified shopping experience
- Review and possibly refine the current service to make it more attractive
In order to achieve these, the chief operating officer of V&P have had a meeting with the store managers to review and discuss the current delivery policy. Here are the notes drafted during the meeting:
- Orders of $80 and above, with weight lower than 10 kg will be delivered for free
- Delivery service is not available if the order value is less than $80.
- Regardless of the amount purchased, delivery service is not available when destination is in an outlying islands.
Some managers believe that there do have more rules other than the four listed above. Unfortunately, they are unable to figure them out especially when the rules weren't documented anywhere, ever. One of the managers suggests to do a bit of analysis by porting the rules into a decision table. Here is the decision table he drew base by transforming the four known rules into table form:
By checking the decision table, one of the managers said, "What about heavier than 10 kg? As I remember, orders weight heavier than 10kg will incur a $10 delivery fee." The managers have been enlightened. They then revised the decision table by adding this new rule. Here is the table updated:
Try it out
- Download the decision table sample project.
- Start Visual Paradigm and open the downloaded project file.
- Open the decision table.
- Base on the case study above, we have to add this rule into the table: "Orders weight heavier than 10kg will incur a $10 delivery fee." The new rule involves a new business decision - request $10 delivery fee. So let's add a new action first. Move the mouse pointer over the compartment caption Actions. Click on the add button near the caption.
- Enter Request $10 delivery fee as action.
- We can now add the rule into the decision table. Similar to adding an action, add a rule by clicking on the add button near the compartment caption Rules.
- Let's express the rule by filling in the conditions and actions cells properly. Under the new rule, double click on the cell for condition Transaction > $80. Select Y in the drop down menu.
- Similarly, put Y for the condition Weight > 10 kg.
- The decision of this rule is to request $10 delivery fee. Mark the action Request $10 delivery fee with X.
-
Let's place the rule next to the second rule so that readers can understand the different business decisions to take when the order is more or less than 10 KG. Right-click on the forth rule and select Move Left from the popup menu.
Finally, the decision table should look like this:
Conclusion
Base on a decision table, you can easily discover hidden rules by evaluating the different combinations of conditions.
Decision table also helps in generating new ideas related to decision making. Continue with the supermarket example, the managers may come up with new rule like: Request for an additional payment when the packed goods is too big in size.
The more thoughtful decision making, the better the business.
