This image was inspired by Nick Broom's post to the DMN group in linked in.
The use case posed by Nick which is here: https://www.linkedin.com/groups/4225568/4225568-6123464175038586884
In the Signavio Decision Modeler’s implementation of DMN, we provide the ability to check whether a set contains an element of another input item or a static set. The expression it uses in the column is an an equivalent of the intersection set operator ∩. The DMN diagram sbove that does this 3 different ways:
1) With the Signavio ‘Multi-Decision’ extension to DMN. This iterates through an input that is a list and checks item by item if the inputs mstch.
2) An internal operator that corresponds to a test of one item or set or items existence as a subset of another using a fixed subset
3) An internal operator that corresponds to a test of one item or set or items existence as a subset of another using an input data type
You do not need the multi decision to support a simple data type list. However, if the input item is a list of complex types (multi attribute types) or complex logic is needed, then the multi-decision is needed.
The Signavio export for this disagram is here.