Semantic Muddle in the Decision Model & Notation (DMN) Standard

Tags: decision management, decision models, decisions, DMN, DMN standard, modeling decisions, standards, TableSpeak
Written by Ronald G. Ross on . Posted in Decision Management, TableSpeak
Tags: decision management, decision models, decisions, DMN, DMN standard, modeling decisions, standards, TableSpeak
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Gary Hallmark
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Ron,
I agree that the the word ‘act’ is problematic. DMN has no actions (no side-effects) and thus, in some sense, cannot ‘act’. A business process might use DMN via a decision service to make some determination and then act upon it. I think in DMN, we want ‘decision’ to capture
1. the determination (outcome)
2. the application of decision logic to required information (decision inputs) to arrive at the outcome. This is purely functional (declarative, if you prefer) with no side-effects.
We should adjust the definition during the beta period.
Ronald G. Ross
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Gary, You said: “DMN has no actions (no side-effects) and thus, in some sense, cannot ‘act’.” Excellent insight! Decision models are something acted *on* (often by software — e.g., a rules engine).
But let me make two observations:
* You present two distinct concepts, not one, that need to be ‘captured’ (I think you mean designated or named). To avoid confusion (‘semantic muddle’) a different term should be used for each concept.
* Use of the term “application” in your second concept presents exactly the same dilemma as for “decision” in the current DMN definition. Here are two definitions for “application” from Merriam Webster Unabridged Dictionary (MWUD). Note the appearance of “act” in the first.
1 : the act of applying: a : the bringing to bear (as of one general statement upon another) by way of elucidation *the application of a theory to a case* b : employment as a means : specific use *the application of certain new techniques*
4 : something applied or used in applying: as a (1) : the part of a discourse in which principles stated previously are applied to practical uses
So does “application” mean the “act” or the thing “applied or used”?
I strongly believe “acts” are completely outside declarative (side-effect-less) logic. So I believe your second concept actually should refer to what in TableSpeak is called “decision logic” (not “decision”).
Gary Hallmark
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No, I don’t think ‘act of applying’ implies side-effects. I suggested ‘application’ only because it does not literally use the word ‘act’ which might connote side-effects to some.
Here, ‘act of applying’ is pure function application. For example, in the decision 0<1 = true, the inputs are the numbers 0 and 1, the logic (a pure function) is '<', and the outcome is true. In DMN, a decision's outcome is determined completely by its inputs and its logic. So you could equally well say the decision is 0<1. But if you say only that the decision is true, you've lost valuable context about where this outcome came from.
Ronald G. Ross
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Gary, The question two questions remain:
1. In a standards specification focused on (side-effect-less) decision logic (not its execution or evaluation by either people or machines), should a “decision” be an “act” or the “result” of an act?
2. Why does the signifier “decision” seem to refer to two distinct concepts in DMN?