DMN 1.3 RTF Avatar
  1. OMG Issue

DMN13 — Enhancement suggestion: make unary tests first class citizens of the FEEL language

  • Key: DMN13-18
  • Status: open  
  • Source: Red Hat Inc ( Edson Tirelli)
  • Summary:

    This is a suggestion for future versions of the spec:

    Add support for Unary Tests as first class citizens of the FEEL language, in a similar way as ranges and functions already are.

    A unary test is really a “predicate”: a single parameter function that returns a boolean. It is syntax sugar on:

    function ( x ) x in <unary_test>

    FEEL already supports functions as first class citizens, so it makes sense to support Unary Tests. The following two syntaxes would then be equivalent:

    is minor : < 18
    is minor : function( age ) age in < 18

    Invoking unary tests explicitly would be like invoking a function:

    Bob is minor : is minor( bob.age )

    More importantly, it would allow the implementation to actually support passing unary tests as parameters to functions and make the example on page 115 viable:

    decision table (
    outputs: "Applicant Risk Rating",
    input expression list: [Applicant Age, Medical History],
    rule list: [
    [ >60, "good", "Medium" ],
    [ >60, "bad", "High" ],
    [ [25..60], -, "Medium" ],
    [ <25, "good", "Low" ],
    [ <25, "bad", "Medium" ]
    ],
    hit policy: "Unique"
    )

    Unary test syntax is not ambiguous, so supporting it would mean to basically change rule 2 in the grammar to include rules 14 and 17 as possible options. The semantic mapping table on page 116 would also need to include a new FEEL value type: "unary test".

  • Reported: DMN 1.1 — Tue, 23 Aug 2016 01:41 GMT
  • Updated: Tue, 6 Aug 2019 19:53 GMT