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Why Model Decisions – it’s not just to write the rules


DMNBookFrontCoverSmallAs you may have noticed I am working on a new book – Available now! Real-World Decision Modeling with DMN – with Jan Purchase. Yesterday Jan had a great blog post – Why Decision Modeling? (In 1000 Words). Jan makes some great points, emphasizing the value of  decision modeling with DMN in:

  • Transparency of the logic
  • Separation  of concerns between processes and decisions
  • Managing Complexity, Maintaining Integrity
  • Agile change of the way we make decisions
  • Standardization of representation
  • Traceability of our implementation

Jan and I are enjoying writing the book. One of the reasons it’s so much fun is that we both agree and bring slightly different perspectives – specifically I tend to spend more of my time building decision requirements models while Jan spends more time drilling the model all the way down to the level of tabular decision logic – decision tables. Reading his post I thought I would add a little additional perspective on the value of decision requirements models.


Decision requirements models are represented with one or more decision requirements diagrams like the one to the right. These show your decision (rectangle), the sub-decisions into which that decision can be decomposed – the other decisions that are required to be made first, the input data (ovals) provided to the decision and the knowledge sources (documents) that contain the know-how you need to make the decisions.

These diagrams are a key element for several of the benefits Jan identified:

  • Transparency: The diagrams are much easier to read than a set of rules would be. I recently built a model to match some existing business rules in a BRMS demo and it was immediately clearer what the decision-making was.
  • Complexity: The diagrams manage complexity in your logic by breaking it down into self-contained pieces that are combined to make a decision.
  • Traceability: Tracing the impact of a change to a policy, shown as a knowledge source, is made much easier as you can walk through the model using the diagram relationships.

But they can do more too.

  • Risk Management
    Even if you don’t plan to write the decision logic, the business rules, for your decision the diagram brings clarity to the way you make decisions. This can be really valuable in a risk management context as it allows a clear definition of the decision-making approach that can be discussed, agreed and even shared with regulators.
  • Training
    We have had several customers take decision requirements models and use them to train front-line decision-makers like claims adjusters or underwriters. The models are more robust and easier to follow than the original document describing the decision.
  • Framing analytics
    When teams are going to use analytics, especially predictive analytics, to improve decision-making it is really important to frame the problem accurately and a model of the decision-making to be improved is perfect for this.
  • Orchestrating Decision Management Systems
    Decision Management Systems often involve business rules, predictive analytics, constraint-based optimization and adaptive control or A/B testing capabilities. How these pieces are being orchestrated to deliver value can be hard for non-technical people to understand – a decision requirements model makes it clear. In our decision modeling tool, DecisionsFirst Modeler, you can even build explicit links from the model to the implementation components.
  • Automation Boundaries
    One of the biggest challenges in automating decisions is determining what to automate and what to leave as a manual decision. A decision requirements model let’s you discuss and agree the decision-making and then consider what makes sense in terms of automation.

The book covers how to build these diagrams, as well as how to write decision logic, and discusses best practices for using these diagrams in all these different situations. Available now! Real-World Decision Modeling with DMNIf you want something to read in the meantime we have a white paper on decision modeling with DMN, some upcoming online training. We also offer services in decision management and decision modeling and you can schedule a free consultation.