Best Practices Series: How to Think about Decisions
Let’s continue with our series on best practices for your decision management projects. We covered what not to do in rule implementation, and what decisions should return. Now, let’s take a step back, and consider how to think about decisions. In other words, I want to focus on the approaches you can take when designing your decisions.
Think about decisions as decision flows
The decision flow approach
People who know me know that I love to cook. To achieve your desired outcome, recipes give you step by step instructions of what to do. This is in my opinion the most natural way to decompose a decision as well. Decision flows are recipes for making a decision.
In the early phases of a project, I like to sit down with the subject matter experts and pick their brain on how they think about the decision at hand. Depending on the customer’s technical knowledge, we draw boxes using a whiteboard or Visio, or directly within the tool. We think about the big picture, and try to be exhaustive in the steps, and sequencing of the steps to reach our decision. In all cases, the visual aid allows experts who have not prior experience in decision management design to join in, and contribute to the success of the project.
What is a decision flow
In short, a decision flow is a diagram that links decision steps together. These links could be direct links, or links with a condition. You may follow all the links that are applicable, or only take the first one that is satisfied. You might even experiment on a step or two to improve your business performance. In this example, starting at the top, you will check that the input is valid. If so, you will go through knock-off rules. If there is no reason to decline this insurance application, we will assess the risk level in order to rate it. Along the way, rules might cause the application to be rejected or referred. In this example, green ball markers identify the actual path for the transaction being processed. You can see that we landed in the Refer decision step. Heatmaps also show how many transactions flow to each bucket. 17% of our transactions are referred.
Advantages of the decision flow approach
The advantage of using this approach is that it reflects the actual flow of your transactions. It mirrors the steps taken in a real life. It makes it easy to retrace transactions with the experts and identify if the logic needs to be updated. Maybe the team missed some exotic paths. maybe the business changed, and the business rules need to be updated. When the decision flow links to actual data, you can use it also as a way to work on your strategies to improve your business outcome. If 17% referral rate is too high, you can work directly with business experts on the path that led to this decision and experiment to improve your outcome.
Think about decisions as dependency diagrams
A little background
In the early days of my career, I worked on a fascinating project for the French government. I implemented an expert system that helped them diagnose problems with missile guidance systems. The experts were certainly capable of layout of the series of steps to assess which piece of equipment was faulty. However, this is not how they were used to think. Conducting all possible tests upfront was not desirable. First, there was a cost to these tests. But more importantly, every test could cause more damage to these very subtle pieces of engineering.
As it was common back then in expert systems design, we thought more in a “backward chaining” way. That means that we reversed engineered our decisions. We collected evidences along the way to narrow down the spectrum of possible conclusions.
If the system was faulty, it could be due to the mechanical parts or to the electronics onboard. If it was mechanical, there were 3 main components. To assess whether it was the first component, we could conduct a simple test. If the test was negative, we could move on to the second component. Etc.
In the end, thinking about dependencies was much more efficient than a linear sequence, for this iterative process.
The dependency diagram approach
Today, the majority of the decision management systems might pale in sophistication compared to this expert system. But the approach taken by experts back then is not so different from the intricate knowledge in the head of experts nowadays in a variety of fields. We see on a regular basis projects that seem better laid out in terms of dependencies. Or at least, it seems more natural to decompose them this way to extract this precious knowledge.
What is a dependency diagram
A dependency diagram starts with the ultimate decision you need to make. The links do not illustrate sequence, as they do in the decision flows. Rather, they illustrate dependencies obviously, showing what input or sub-decision needs to feed into the higher level decision. In this example, we want to determine the risk level, health-wise, of a member in a wellness program. Many different aspects feed into the final determination. From a concrete perspective, we could look at obesity, blood pressure, diabetes, and other medical conditions to assess the current state. From a subjective perspective, we could assess aggravating or improving factors like activity and nutrition. For each factor, we would look at specific data points. Height and weight will determine BMI, which determines obesity.
Similarly to the expert system, there is no right or wrong sequence. Lots of factors help make the final decision, and they will be assessed independently. One key difference is that we do not diagnose the person here. We can consider all data feeds to make the best final decision. Branches are not competing in the diagram, they contribute to a common goal. The resulting diagram is what we call a decision model.
Advantages of the dependency diagram approach
Dependency diagrams are wonderful ways to extract knowledge. As you construct your decision model, you decompose a large problem into smaller problems, for which several experts in their own domain can contribute their knowledge. When decisions are not linear, and the decision logic has not yet been documented, this is the right approach.
This approach is commonly used in the industry. OMG has standardized the notation under the “DMN” label, which stands for Decision Model and Notation. This approach allows you to harvest knowledge, and document source rules.
Choose the approach that is best for you
Decision flows are closest to an actual implementation. In contrast, dependency diagrams, or decision models, focus on knowledge. But they feed straight into decision management systems. In the end, think about decisions in the way that best fits your team and project. The end result will translate into an executable decision flow no matter what.