Semantic Muddle in the Decision Model & Notation (DMN) Standard
Comment by DMN proponent: In common business use the term “decision” is often overloaded to mean “decision output”. So I “make a decision to do X” is the act, whereas I “use the decision as input to another decision” is referring to the decision output. I’m not sure there are any semantic issues with (i.e. possible problems caused by) this overloading?
My response: Since DMN is a standard (and in particular claims to be a business standard), then it must stick with its own definition of terms in all cases. Otherwise, in what sense is it a standard (especially a business standard)?
In defining “decision” DMN had two fundamental choices (from Merriam-Webster Unabridged dictionary):
1. a : the act of deciding; specifically : the act of settling or terminating (as a contest or controversy) by giving judgment
1. b : a determination arrived at after consideration : SETTLEMENT, CONCLUSION
DMN explicitly chose the first meaning. I strongly prefer the second, but then I’m a big fan of all things declarative. So in BRS TableSpeak[1] an outcome by definition is a decision.
Since DMN explicitly chose the first meaning, however, an outcome (conclusion) is by definition *not* a decision. A decision is an act, never the result of the act.
Hey, I’m just reading what is written in the standard. If DMN somehow allows ‘overloading’ of the term “decision” — the central term in the standard — all bets are off. A term that you can use any way you want when it happens to suit you is a term that has not been standardized at all. The result is semantic muddle. Pretty big deal. Sorry!
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Tags: decision management, decision models, decisions, DMN, DMN standard, modeling decisions, standards, TableSpeak
Ronald G. Ross
Ron Ross, Principal and Co-Founder of Business Rules Solutions, LLC, is internationally acknowledged as the “father of business rules.” Recognizing early on the importance of independently managed business rules for business operations and architecture, he has pioneered innovative techniques and standards since the mid-1980s. He wrote the industry’s first book on business rules in 1994.
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?