DMN Decision Literal Expression
A decision literal expression represents decision logic which can be depicted as an expression in DMN 1.1. It consists of a literal expression and a variable.
A decision literal expression is represented by a literalExpression
element inside a decision
XML element.
<definitions xmlns="http://www.omg.org/spec/DMN/20151101/dmn.xsd" id="definitions" name="definitions" namespace="http://camunda.org/schema/1.0/dmn">
<decision id="season" name="Season">
<variable name="season" typeRef="string" />
<literalExpression>
<text>calendar.getSeason(date)</text>
</literalExpression>
</decision>
</definitions>
Decision Name
The name describes the decision for which the literal expression provides the
decision logic. It is set as the name
attribute on the decision
element.
<decision id="season" name="Season">
<!-- ... -->
</decision>
Decision Id
The id is the technical identifier of the decision. It is set in the id
attribute on the decision
element.
Each decision should have an unique id when it is deployed to the Camunda BPM
platform. The engine uses the id as the decision key of the deployed
DecisionDefinition
.
<decision id="season" name="Season">
<!-- ... -->
</decision>
Literal Expression
The literal expression specifies how the value of the decision is generated. It is an expression which will be evaluated by the DMN engine. It can be used to do a complex calculation, to invoke a bean which provides decision logic, or to combine the output values of required decisions.
The expression is set inside a text
element that is a child of the literalExpression
XML element.
<literalExpression>
<text>calendar.getSeason(date)</text>
</literalExpression>
Literal Expression Language
The expression language of the literal expression can be specified by the
expressionLanguage
attribute on the literalExpression
XML element. The
supported expression languages are listed in the User Guide.
<literalExpression expressionLanguage="groovy">
<text>calendar.getSeason(date)</text>
</literalExpression>
If no expression language is set then the global expression language is used
which is set on the definitions
XML element.
<definitions id="definitions"
name="definitions"
xmlns="http://www.omg.org/spec/DMN/20151101/dmn.xsd"
expressionLanguage="groovy"
namespace="http://camunda.org/schema/1.0/dmn">
<!-- ... -->
</definitions>
In case no global expression language is set, the default expression language is used instead. The default expression language for literal expressions is JUEL. Please refer to the User Guide to read more about expression languages.
Variable
A decision literal expression must have a variable which specifies the name and the type of the decision result.
A variable is represented by a variable
element inside a decision
XML element.
<decision id="season" name="Season">
<variable name="season" />
</decision>
Variable Name
The name of the variable is used to reference the value of the literal expression in the decision result. It is specified by the name
attribute on the variable
XML element.
<variable name="season" />
Variable Type Definition
The type of the decision result can be specified by the typeRef
attribute on the
variable
XML element. After the expression is evaluated by the
DMN engine it converts the result to the specified type. The supported types
are listed in the User Guide.
<variable name="season" typeRef="string" />
Note that the type is not required but recommended since it provides a type safety of the expression result.