Design5 min read

Decision tables with DMN and FEEL

Move business rules out of code and into a table anyone can read: build a discount table, test it, and call it from a process.

In short

01
Rules live in a table, not in gateway conditions or worker code.
02
Test a table with sample values before a process uses it.
03
A business rule task runs the table and stores its outputs as variables.

A decision table takes input values, finds the rule that matches, and returns outputs. DMN is the standard for the table; FEEL is the small expression language used inside its cells.

Example: a discount table

Region	Amount	→ Discount
"EU"	> 1000	0.2
"EU"	-	0.05
-	-	0

Read each row as a rule. An EU order above 1000 gets 20%; any other EU order gets 5%; everything else gets nothing. A dash means "any value".

What goes in a cell

Cell	Meaning
"EU"	Equals the text EU
> 1000	Greater than 1000 (also <, >=, <=, !=)
[100..500]	Between 100 and 500
-	Matches anything
amount * 0.1	An output can be a calculation

Hit policies

The hit policy decides what happens when more than one rule matches. Orkovia supports the nine DMN hit policies — for example Unique (only one rule may match), First (the first matching rule wins) and Collect (return every match).

Build, test, use

Build the table in Studio

Add input and output columns, then rules. You can also import an existing .dmn file.

Test it

Evaluate the table with sample values. The trace view shows which rules matched and why.

Call it from a process

Add a business rule task and point it at the decision. When the task runs, every output column becomes a process variable.

curl -X POST http://localhost:3000/api/v1/decisions/<id>/evaluate \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"variables": {"region": "EU", "amount": 1500}}'

Decision tables, literal expressions, decision requirement graphs and decision services are supported. Boxed context, invocation and relation expressions are not yet.

See it on your own process

Book a walkthrough with the Orkovia team.

Request a Demo

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