Newcomers to the Decision Model and Notation (DMN) standard may be put off by the notion of a decision table's "hit policy." What the heck is that? It sounds technical. Add to that the idea that the modeler is supposed to select the "best" one. Too complicated! Well, it's actually not. Here is what's going on. Each row in a decision table is a rule. The columns represent inputs and, at the end, one (or occasionally more than one) output.
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Decision logic can take many forms: constraint rules, if-then rules, decision trees, decision tables, and more. Over the years, decision management vendors have gradually allowed decision tables to nudge the other forms aside, for a number of reasons. Decision tables are easy for business people to understand. Their logic is declarative, meaning there is no prescribed order of evaluation. They can be analyzed, either by visual inspection or software, for completeness and consistency, meaning every combination of input values generates a consistent outcome regardless of the order of evaluation.
Recently I posted about the looming New Era of decision management. Some will say, "Yes, we know. You've been touting DMN for a year now." That is true. But this week something changed. What changed is the release of the first complete implementation of the standard, from Trisotech. Their crack marketing staff assigned it version number 5.1.10, like it's nothing much. But trust me, it's a big deal. Let me explain why.
Today I am launching a brand new version of DMN Method and Style Basics training. This one is based on the latest iteration of Trisotech DMN Modeler, which is the first software available to support all five of DMN's key elements: DRDs Decision tables FEEL, including all built-in functions and operators Boxed expressions, all of them: invocation, context, relation, plus of course literal expression and decision table XML interchange, per the DMN standard Oh, and did I mention execution?
Today the world of decision management finds itself in roughly the position of business process management a decade ago: A shrinking number of highly optimized tools and runtime engines, each with its own modeling notation and execution language, struggling with inefficient translation of "business requirements" into executable decision logic. The solution then for BPM vendors was to unify modeling and execution in a single tool-independent language based on a standard diagramming notation.
Every discussion of DMN these days seems to begin with some declaration of what “business users don’t like.” They don’t like FEEL. They don’t like boxed expressions. They don’t like BKMs. They don’t like contexts. They don’t like names with underscores, or, heaven forbid, camel case! They don’t like parentheses to define a numeric interval excluding the endpoints. They don’t like hipsters, Obamacare, or Hillary’s email server. What they do like about DMN, by universal agreement, is its use in classification decisions.
With the Decision Model and Notation (DMN) standard, the Object Management Group (OMG) is hoping to replicate its signature success story, BPMN. Unlike most OMG standards, both BPMN and DMN are purportedly aimed at business users rather than developers and architects. Business users are notoriously averse to standards, so BPMN’s achievement of high business user adoption is surprising. Naturally, that success has spawned legions of critics as well, who say it’s too complicated for business users, too many icons and symbols, too many rules for what’s correct and incorrect.
This post is a transcript of my keynote at RuleML/DecisionCamp on July 8, 2016. I was surprised to be invited to speak here about DMN, because the inventors of DMN are here in the room but I am not one of them. While they were off inventing DMN, I was working in the related area of business process management, most recently focused on business process modeling using BPMN. But that background is relevant to my talk today because DMN, the new decision modeling standard from the Object Management Group (OMG), is now attempting to replicate the success of BPMN.
This post is based on a talk I gave at the BBC conference in November. DMN, which stands for Decision Model and Notation, is a relatively new OMG standard. By unifying business decision modeling and execution, it hopes to do for Business Decision Management what BPMN did for BPM over the past decade, which is radically transform the business. Like BPMN, it is intended for business analysts and business users, not programmers.