DMNFTF — Extend Priority hit policy to multiple-output tables

Priority and Output order hit policies are not supported for compound output tables.

Jacob Feldman commented in the LinkedIn DMN group:

"Building real-world decision models, practitioners always face complex issues related to diagnostic and resolution of rule conflicts. Some systems can effectively verify decision model consistency and diagnose rule conflicts. But until recently there were no practically used BR products that claim that they may automatically resolve rule conflicts.

"While we did not had an update about the current state of the DMN for a while, it does not seem that the first version will include any means to define superiority relations among contradictory rules. I believe at some point DMN may and should be extended in this direction."

(This was functionality I originally wanted, too, but for some reason we did not cover it in v1.)

The example he provides could be handled by a very simple extension to DMN (see attached file). I propose we extend the Priority and Output order hit policies to compound output decision tables, by making the first output column the Priority marker regardless of how many columns there are.

In clause 8.2.11, replace:

"To reduce complexity, decision tables with compound outputs support only the following hit policies: Unique, Any, First, Rule order and Collect without operator, because the priority schema or collect operator over multiple outputs are undefined."

with the attached.