Introduction to FEEL

Contents

◷ Reading Time: 3 minutes

The expression language of DMN is the Friendly Enough Expression Language (FEEL). FEEL is written to be useable by both business and IT professionals.

FEEL is designed to be easy to read and intuitive, with comparison and logical operators acting how you would think they should.

Take a look in this example written using FEEL:

2 >= 1 and false != true and "string" = "string"

As you can see it is easy to tell what is going on. We have three boolean comparisons anded together. Each comparison is true, which gives us true and true and true so the returned result is true

Let’s look at another example:

if (2 >= 1 and false != true and "string" = "string") then "Three True Comparisons" else null

Here we’re using an if else structure. If the three boolean comparisons result in true then return the string “Three True Comparisons” else return null.

After reading this article you’ll be able to open the Interactive Shell and test them out yourself.

Learning FEEL

To understand FEEL and how it is integrated into FlexRule, refer to these resources:

FEEL Expressions is a great place to start learning how FEEL works. It offers a list of expressions in FEEL with examples
For FEEL expressions that have to do with Date and Time, check out FEEL Date and Time Expressions
DMN Functions is a list of DMN functions that can be used with FEEL with expressions