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Decision requirements graph

Decision Requirements Graph

A Decision Requirements Graph (DRG) models a domain of decision-making, showing the most important elements involved in it and the dependencies between them. The elements modeled are decisions, input data, and knowledge sources.

The visual representation of a DRG is called Decision Requirements Diagram (DRD).

In the XML a DRG is represented by the definitions element.


<definitions xmlns="https://www.omg.org/spec/DMN/20191111/MODEL/" id="dinnerDecisions" name="Dinner Decisions"
             namespace="http://camunda.org/schema/1.0/dmn">
    <decision id="dish" name="Dish">
        <!-- ... -->
    </decision>
    <decision id="beverages" name="Beverages">
        <!-- ... -->
    </decision>
</definitions>

Decision requirements graph name​

Decision Requirements Graph Name

The name describes the DRG. It is set as the name attribute on the definitions element.


<definitions xmlns="https://www.omg.org/spec/DMN/20191111/MODEL/"
             id="dinnerDecisions"
             name="Dinner Decisions"
             namespace="http://camunda.org/schema/1.0/dmn">
    <!-- ... -->
</definitions>

Decision requirements graph id​

Decision Requirements Graph Id

The id is the technical identifier of the DRG. It is set in the id attribute on the definitions element.

Each DRG should have an unique id when it is deployed to Camunda.


<definitions xmlns="https://www.omg.org/spec/DMN/20191111/MODEL/"
             id="dinnerDecisions"
             name="Dinner Decisions"
             namespace="http://camunda.org/schema/1.0/dmn">
    <!-- ... -->
</definitions>

Decision​

Decision

A decision requirements graph can have one or more decisions. A decision has a name which is shown in the DRD and an id. The decision logic inside the decision must be either a decision table or a decision literal expression.

A decision is represented by a decision element inside the definitions XML element.


<definitions xmlns="https://www.omg.org/spec/DMN/20191111/MODEL/" id="dish" name="Desired Dish" namespace="party">
    <decision id="beverages" name="Beverages">
        <decisionTable id="decisionTable">
            <!-- ... -->
        </decisionTable>
    </decision>
</definitions>

Required decisions​

Required Decision

A decision can have one or more required decisions which it depends on.

A required decision is represented by a requiredDecision element inside an informationRequirement XML element. It has a href attribute and the value starts with # followed by the decision id of the required decision.

tip

The result of a required decision can be accessed in the dependent decision by its decision id.

If the required decision is a decision table and has more than one output then the output values are grouped under the decision id and can be accessed by their output names ( e.g. decisionId.outputName). The structure of the result depends on the decision table hit policy.


<decision id="beverages" name="Beverages">
    <informationRequirement>
        <requiredDecision href="#dish"/>
    </informationRequirement>
    <!-- ... -->
</decision>

Input data​

Input Data

An input data denotes information used as an input by one or more decisions.

It is represented by an inputData element inside the definitions element.


<definitions xmlns="https://www.omg.org/spec/DMN/20191111/MODEL/" id="dinnerDecisions" name="Dinner Decisions"
             namespace="http://camunda.org/schema/1.0/dmn">
    <inputData id="guestsWithChildren" name="Guests with children?"/>

    <decision id="beverages" name="Beverages">
    <informationRequirement>
        <requiredInput href="#guestsWithChildren"/>
    </informationRequirement>
    <!-- ... -->
</definitions>

Note that an input data has no execution semantics and is ignored on the evaluation.

Knowledge source​

Knowledge Source

A knowledge source denotes an authority for a Decision.

It is represented by a knowledgeSource element inside the definitions element.


<definitions xmlns="https://www.omg.org/spec/DMN/20191111/MODEL/" id="dinnerDecisions" name="Dinner Decisions"
             namespace="http://camunda.org/schema/1.0/dmn">
    <knowledgeSource id="cookbook" name="Men's Cookbook"/>

    <decision id="dish" name="Dish">
    <authorityRequirement>
        <requiredDecision href="#cookbook"/>
    </authorityRequirement>
    <!-- ... -->
</definitions>

Note that a knowledge source has no execution semantics and is ignored on the evaluation.