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  1. OMG Issue

DMN13 — mix up of list and non-list in filter expression example

  • Key: DMN13-29
  • Status: open  
  • Source: Signavio GmbH ( Bastian Steinert)
  • Summary:

    Section 10.3.2.5 includes a few examples for the filter expression. In particular it shows the following example:
    [

    {x:1, y:2}

    ,

    {x:2, y:3}

    ][x=1] =

    {x:1, y:2}

    The result of this expression is a context (an object). I first thought this must be a mistake, as the filter expression should always return a list.

    I then found the following sentence: 'Singleton lists are equal to their single item.', showing that the above expression returns a non-list value by intention.

    I wonder how the need for mixing up lists and non-list (with the so called singleton list) has arisen. I have never seem something like it before and I have difficulties to see its value. In addition, I could not find a second sentence in the entire standard that also uses or describes the concept of singleton lists.

    Therefore, I would like to propose removing this single sentence about singleton-lists and would like to change the example to look like this:
    [

    {x:1, y:2}

    ,

    {x:2, y:3}

    ][x=1] = [

    {x:1, y:2}

    ]

  • Reported: DMN 1.1 — Tue, 1 Nov 2016 13:03 GMT
  • Updated: Fri, 21 Dec 2018 15:24 GMT