DMN notation reference
DMN is much smaller than BPMN: a decision requirement diagram showing structure, and decision tables holding the logic, with FEEL expressions in the cells.
The hit policy is the piece to understand first, because it is the piece that changes behaviour.
#When it matters
Authoring decision tables that somebody else will maintain.
Reviewing rules for overlaps and gaps.
Connecting decisions to BPMN business rule tasks.
#The symbols
Symbol | Means |
|---|---|
Decision requirement diagram | The map: decisions, inputs and authorities. |
Decision table | The logic: inputs, outputs, rules, hit policy. |
FEEL | The expression language inside the cells. |
Hit policy | What happens when more than one rule matches. |
#A few things that catch people out
Draw the requirement diagram before writing tables; it tells you how many you need.
Unique is the safest hit policy, because overlap becomes a visible error.
A dash in a cell means the input is irrelevant, not that it is empty.
#Related
The notation is the meaning.
