What is DMN?

The Decision Model and Notation (DMN) enables you to document decision processes in a structured and formalized manner involved stakeholders can easily understand. The specification documents of the standard can be found at http://www.omg.org/spec/DMN/1.0/

Although DMN is an independent notation, it is designed to enable linking DMN to BPMN diagrams. This can be of great value, as DMN complements BPMN perfectly when it comes to modeling complex design processes. DMN modeling helps you to prevent messy BPMN decision process structures like the one sketched out below:

../../_images/bpmnmess_en.png

Modeling decision process in BPMN can create overly complex processes.

DMN element structures are called Decision Requirements Graphs (DRG). They form Decision Requirements Diagrams (DRD).

Decision requirement graphs use the following simple set of components:

Elements

There are four different core elements in DMN: Decisions, Input Data, Business Knowledge Models and Knowledge Sources:

Decision

The 'Decision' element

The ‘Decision’ element

Decisions depict a point where an output is determined from one or several inputs, making use of decision logic. Decisions may require one or multiple Business Knowledge Model elements.

Input Data

The 'Input Data' element

The ‘Input Data’ element

Input Data elements contain information which is used by one or several Decision and/or Business Knowledge Model elements.

Business Knowledge Model

The 'Business Knowledge Model' element

The ‘Business Knowledge Model’ element

Business Knowledge Models are functions providing logic for one or multiple Decision elements.

Knowledge Source

The 'Knowledge Source' element

The ‘Knowledge Source’ element

A Knowledge Source depicts an authority, which has to be considered during a decision or business model function.

Requirements (Connectors)

DMN connectors in the Signavio editor

DMN connectors in the Signavio Editor.

There a three types of connectors in DMN. All of these connectors establish a requirement relationship: The element the connector is pointing to requires the input of the connector’s source. Thus, in DMN connectors are drawn from the receiving (or requiring) element to the starting point, contrary to connectors in BPMN diagrams, which are drawn from the source to the target element.

Information Requirement

An Information Requirement connector starts at a Data Input or Decision element and points to the Decision element that requires the information.

Knowledge Requirement

A Knowledge Requirement connector starts at a Business Knowledge Model and points to a Decision or a Business Knowledge Model element that needs the information.

Authority Requirement

An Authority Requirement points from an Input Data element to a dependent Knowledge Source or from a Knowledge Source to any dependent decision requirement graph element.

Decision Rules

Both Decision and Business Knowledge Model elements contain decision logic tables.

Decision logic tables transform

inputs with the help of

rules into

outputs and can be depicted like this:

A decision logic table in the Signavio editor

A decision logic table in the Signavio Editor.

A complete decision requirements graph could for example look like this:

An example of a DMN diagram

An example of a DMN diagram