DMN12 — Graphical representation of Context - "sub-DRDs"

This issue is meant to factor-out the "sub-DRD issue" from a number of issues (DMN12-27, DMN12-38) that are actually independent of whether we have "sub-DRDs". There may be better ways or alternate ways of expressing notation and meaning of a 'DRD in a box' but this seems to be a recurring theme so similar issues or competing proposals should be linked here for comparison.

Context is an important form of value expression but tool vendors appear reluctant to implement it, believing it to be not as business-friendly as a DRD expressing the same logic. I propose that DMN 1.2 add a graphical representation of a context, in which nodes represent a context entries, linked by information requirements. A decision whose value expression is a context represented in this way would be indicated in the DRD with a special marker.

The benefits of such a change are these:
1. Increased support for Contexts by tool vendors
2. More business-friendly representation
3. Simpler “top-level” DRD representation of complex end-to-end logic
4. Reusability of more complex decision logic, since BKMs can visualize their value expression in this way.
5. Compatibility with Bastian’s MID proposal 12-27.

Invocable decision service addresses this issue

See DMN12-10