Camunda Platform 7.13

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FEEL Language Elements

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This page provides information on the legacy FEEL Engine, that was used before the current Scala-based FEEL Engine was integrated into the Camunda Platform.

The Camunda DMN engine supports FEEL for input entries. The FEEL term for expression in input entries are simple unary tests. These simple unary tests test an input value against an expression and return either true if the test is satisfied or false otherwise. The expression can contain different elements which are described in this sections.

Comparison

FEEL simple unary tests support the following comparison operators. Please note that the equals operator is empty and not =. Also, a non equal operator such as != does not exist. To express this, negation has to be used.

Name Operator Example Description
Equal "Steak" Test that the input value is equal to the given value.
Less < < 10 Test that the input value is less than the given value.
Less or Equal <= <= 10 Test that the input value is less than or equal to the given value.
Greater > > 10 Test that the input value is greater than the given value.
Greater or Equal >= >= 10 Test that the input value is greater than or equal to the given value.

Range

Some FEEL data types, such as numeric types and date types, can be tested against a range of values. These ranges consist of a start value and an end value. The range specifies if the start and end value is included in the range.

Start End Example Description
include include [1..10] Test that the input value is greater than or equal to the start value and less than or equal to the end value.
exclude include ]1..10] or (1..10] Test that the input value is greater than the start value and less than or equal to the end value.
include exclude [1..10[ or [1..10) Test that the input value is greater than or equal to the start value and less than the end value.
exclude exclude ]1..10[ or (1..10) Test that the input value is greater than the start value and less than the end value.

Disjunction

A FEEL simple unary test can be specified as conjunction of expressions. These expressions have to either have comparisons or ranges. The test is true if at least one of conjunct expressions is true.

Examples:

  • 3,5,7: Test if the input is either 3, 5 or 7
  • <2,>10: Test if the input is either less than 2 or greater than 10
  • 10,[20..30]: Test if the input is either 10 or between 20 and 30
  • "Spareribs","Steak","Stew": Test if the input is either the String Spareribs, Steak or Stew
  • date and time("2015-11-30T12:00:00"),date and time("2015-12-01T12:00:00"): Test if the input is either the date November 30th, 2015 at 12:00:00 o’clock or December 1st, 2015 at 12:00:00 o’clock
  • >customer.age,>21: Test if the input is either greater than the age property of the variable customer or greater than 21

Negation

A FEEL simple unary test can be negated with the not function. This means if the containing expression returns true, the test will return false. Please note that only one negation as first operator is allowed but it can contain a disjunction.

Examples:

  • not("Steak"): Test if the input is not the String Steak
  • not(>10): Test if the input is not greater than 10, which means it is less than or equal to 10
  • not(3,5,7): Test if the input is neither 3, 5 nor 7
  • not([20..30]): Test if the input is not between 20 and 30

Qualified Names

FEEL simple unary tests can access variables and object properties by qualified names.

Examples:

  • x: Test if the input is equal to the variable x
  • >= x: Test if the input is greater than or equal to the variable x
  • < customer.age: Test if the input is less than the age property of the variable customer

Date Functions

FEEL simple unary tests provide functions to create date types. The Camunda DMN engine supports the following date functions:

  • date and time("..."): Creates a date and time value from a String with the format yyyy-MM-dd'T'HH:mm:ss

Examples:

  • date and time("2015-11-30T12:00:00"): Test if the input is the date November 30th, 2015 at 12:00:00 o’clock
  • [date and time("2015-11-30T12:00:00")..date and time("2015-12-01T12:00:00")]: Test if the input is between the date November 30th, 2015 at 12:00:00 o’clock and December 1st, 2015 at 12:00:00 o’clock

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