DMN decision table structure

A decision table has a fixed anatomy: input columns on the left, output columns on the right, one rule per row, and the hit policy in the top-left corner.

Once you can read that layout, every DMN table in the world reads the same way.

#When it matters

Reading somebody else's decision table.
Designing one that a business owner will maintain.

#The symbols

Symbol	Means
Hit policy	Top-left corner. Decides what happens on multiple matches.
Input columns	Left. One per input, with its type.
Output columns	Right. One or more results.
Rules	One per row, read left to right.
Annotations	Right-most column. Notes that do not affect the result.

#A few things that catch people out

Column order does not affect the result, but it affects readability. Put the most decisive input first.
Every rule needs a value or a dash in every input column.
If the table has one input column, you probably wanted a decision tree.

DMN requirement elements

What feeds what, above the tables.

DMN hit policies

What happens when two rules match.

DMN notation reference

Back to the full DMN reference.

Pick the hit policy on purpose.