# Decision table

A decision table is the right shape when a decision depends on several inputs at once. Drawn as a tree it explodes; written as a table it stays one screen.

Capable includes a DMN editor, so the table you author is a real DMN decision with hit policies and FEEL expressions, not a picture of a spreadsheet.

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## When to reach for one

* Pricing, eligibility and discount rules with several inputs.
* Anything a business analyst will maintain after you have moved on.
* Decisions that will later be executed by a rules engine.

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## How to draw it in Capable

| **Route**    | **Use when**                                             |
| ------------ | -------------------------------------------------------- |
| DMN editor   | Always, for a real decision table.                       |
| A page table | Only when the rules will never be executed or validated. |

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## Hit policies worth knowing

| **Policy** | **Meaning**                                                             |
| ---------- | ----------------------------------------------------------------------- |
| Unique     | Exactly one row may match. Two matches is an error, and that is useful. |
| First      | Rows are ordered; the first match wins.                                 |
| Collect    | Every match contributes, optionally summed or counted.                  |
| Any        | Several rows may match, but they must agree on the output.              |

⚠️

**Unique is the safest default.** It turns overlapping rules into a visible error rather than a silent, order-dependent answer.

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## A few things that catch people out

* The hit policy is not decoration. Unique, First and Collect behave differently when two rows match.
* FEEL expressions let a cell say \[18..65\] or not("UK"), which a plain table cannot.
* A DMN table with one input column is a decision tree wearing a disguise.

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## Related

[Value stream mapWhere the time actually goes.](https://help.gocapable.com/diagrams/value-stream-map.html)

[User flow diagramScreen by screen, including the dead ends.](https://help.gocapable.com/diagrams/user-flow-diagram.html)

[ExamplesWorking diagrams you can copy.](https://help.gocapable.com/diagrams/examples.html)

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_Draw the unhappy path too._