Literal Expression

This icon in the top right corner of the Decision or Business Knowledge  Model (BKM) element indicates that it is implemented as a Literal Expression. A Literal Expression is the simplest form of DMN expression. It is commonly defined as a single-line statement or an if-else conditional block. When an expression becomes more complex, a modeler might choose a Boxed Context in preference to a Literal Expression, or in order to improve the readability the modeler could encapsulate some of the logic as a function in the DMN Library. The Literal Expression is a type of value expression used in both Decision and Business Knowledge Model (BKM) elements.

This image shows the key parts of the DMN Expression window for the definition of Literal Expressions. Recall that there are three other types of value expression and the window will appear differently for each of these.

The Literal Expression is a textual representation of the decision logic.  It describes how an output value is derived from its input values, using mathematical and logical operations.

The DMN Expression window presents the Literal Expression as a table, with two key rows:

• Parameters:  defines the input parameters used in the expression
• Literal Expression:  where the formula for the expression is defined - this defines the output of the Decision

In order to support simulation and execution, the Literal Expression can use JavaScript global functions or JavaScript object functions.  Users can also create DMN Library functions for use within the expressions.