What Is DMN?

DMN, which stands for Decision Model and Notation, is a standard managed by OMG, the organization behind BPMN.  It is trying to do for Business Decision Management what BPMN did for Business Process Management a decade ago: empower the business to take charge of the logic that drives its operations, through a vendor-independent diagramming language.  Actually, DMN goes further than BPMN by empowering business users to create fully executable decision services using diagrams and tables, not programming… what today we call Low-Code.  The Trisotech Digital Enterprise Suite, the platform we use in our training, borrows DMN’s Low-Code features for use in BPMN, making fully executable process services Low-Code as well, enabling Low-Code Business Automation based entirely on standards.  Actually, DMN should be considered a Low-Code language for any type of business logic, not just what we normally consider business decision logic.

The seeds of DMN were planted a decade ago in the “Decisions First” rebellion against the traditional practice of business rules management, in which decisions were assembled bottom-up from thousands of rules “harvested” from spreadsheets, legacy COBOL, and policy manuals for centralized management and automation.  Decisions First instead asked business to understand the decisions needed for everyday operations, and from those determine the information required to make them.  The new top-down decomposition of complex decision logic into a network of simpler supporting decisions, down to source input data, became the basis of DMN’s Decision Requirements Diagrams.  Rectangles in the DRD represent decisions, and their incoming solid arrows, called information requirements, represent the inputs to their decision logic.

But DMN defines more than just decision requirements.  It also provides a Low-Code language for the logic inside each decision, the value expression that maps the decision’s inputs to its output value.  That language is model-based, not code.  It relies on standardized tabular formats called boxed expressions, and a powerful but business-friendly expression language called FEEL for the formulas inside the table cells.  The most well-known boxed expression type is called a decision table.  Decision tables long predated DMN, but DMN places strict rules around their format and syntax.  But you cannot fully define decision logic with decision tables alone.  DMN in addition provides a number of other boxed expressions: literal expression, invocation, context, relation, and more.  A tool that fully implements DMN, such as Trisotech Decision Modeler, must support all the boxed expressions and FEEL.

DMN is an open standard.  Like BPMN, its concepts and formats are not the protected intellectual property of a tool vendor or consulting firm.  DMN 1.0 was published officially in September 2015, and it continues to be revised and updated by the DMN Revision Task Force in OMG.  Our current DMN training is based on DMN 1.4, and the RTF is currently working on DMN 1.5, due sometime in 2023.