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Is a Decision-Based Approach Sufficient for Business Rules?

Consider the following example.

Behavioral Rule: A student with a failing grade must not be an active member of a sports team.

This business rule:    
  • Is not about selecting the most appropriate sports team for a student – i.e., not about the decision, Which sport team is best for a student?.
  • Does not apply only at a single point of determination – e.g., when a student joins a team.
Instead, the business rule is meant to be enforced continuously – for example, if a student who is already active on some sports team should let his or her grades fall. What’s the business decision for when a student’s grades fall and they should be taken off a team? Be real, there’s no good answer to that question. This example is no outlier. Businesses have 1,000s of behavioral rules like this. Let’s be clear – I believe a business-decision-based approach is very powerful for decision rules. I have written much about that. And I don’t disagree that many business-rule projects have floundered due to lack of pragmatic organizing principles (e.g., “decisions”). But if you take a decision approach to behavioral business rules, either it will prove woefully incomplete with respect to integrity, or you’ll quickly start to drown in (system-level) decisions. In my opinion, an application that has to be designed and to operate to treat violations of behavioral rules as just more decisions is not a smart enough system. The detection of violation events for behavioral rules can be, and should be, completely under the covers (identified, detected and supported by a platform). Otherwise the solution won’t scale. And there will be so many decision dependencies it will steal from the very real value of a business-decision-based approach. This frankly is a sign of immaturity … or lack of imaginative leadership … or IT bias … or whatever … in some parts of the decision-model community. The detection of a violation of a behavioral rule is an event, not a decision. A business decision is a business decision; a system decision is … well … why even go there?! P.S. There are 3 specific examples and more complete discussion about this topic on http://goo.gl/NCnLi.      

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Ronald G. Ross

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.

Comments (5)

  • Han Joosten

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    Hi Ron,

    The difference between behavior rules and decision rules is an important one. Did you hear about the Ampersand approach? It is a method to derive processes by making explicit the set of behavior rules that define the process.
    It is useful to divide behavior rules into invariants (rules that may not be violated at any time) and process rules (rules that can be violated temporarily). Let me explain, based on the example you gave.
    If the rule is strictly enforced, then there cannot be a student with a failing grade being an active member of a sports team. This means, that a student with a failing grade cannot become an active member of a sports team. Any attempt would be rejected by the system that enforces the rule. Also, an active member of a sports team cannot become a student with a failing grade. (Interesting, for in that case a good precaution to not having a failing grade would be to make sure you are an active member of a sports team 😉 ).
    The other type of behavior rule is the one that may be (temporarily) violated. Any such rule must have a role defined to it that is responsible for acting upon violations. In our example, even an active member of a sports team could become a student with a failing grade, and a student with a failing grade could become an active member of a sports team. However, each violation would be signaled to the responsible for the rule, whom can act on it.
    Ampersand offers a means to derive a design of a system based on these rules. Each rule is expressed both in natural language as well as in a formal relation algebra expression. The natural language is to ensure that the business is fully in control of their rules; the formal expression is to guarantee that the rule is based on a consistent set of fact types, and thus the total set of rules is internally consistent.
    Want to know more? Have a look at ampersand.sourceforge.net
    Kind regards,
    Han Joosten, rules consultant.

    • Ronald G. Ross

      Ronald G. Ross

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      Han, Interesting. But there is really a range of possibilities in enforcement levels for behavioral rules beyond the two you mention. See Business Rule Concepts (4th ed), p. 135.

  • Nick Broom

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    Hi Ron,

    I’ve read a number of related posts on this topic that you’ve posted in a few places and wanted to step through the thoughts I’ve had in trying to get the distinction clear in my own mind between the two rule types.

    So first off, I’ve not been doing business rules as long as your good self, so forgive any semantic slip-ups that I make in any of the following paragraphs!

    The example you give here and on your extract from Decision Analysis — A Primer: How to Use DecisionSpeak™ and Question Charts (Q-Charts™) at http://www.brcommunity.com/ross.php is the kind of thing I would have treated as a policy; the type of wording you would find in terms & conditions associated to a product, or the standards set out by a university. So to that end, yes, I can see how one would state that they need to be evaluated ‘continuously’.

    In practice though, how ‘continuously’ does a rule get evaluated? Setting the behavioural rule is one thing, enforcing it is another. Whilst there may be multiple determination points for the evaluation of a behavioural business rules, each determination point is still distinct in its own right and the method of determination will depend on the context. Using this example, a teacher may evaluate the rule when reviewing the marks of the student after a monthly test. If the grades have dropped from one review session to the next, then you might expect them to see whether they are a member of a sports team and, if so, enforce the rule by the appropriate action. They may also choose to invoke any remedial action required to get the student back on track.

    Equally, the rule may be evaluated when a sports team is being selected. Let’s say in this instance that the teacher has not yet reviewed the student’s grades, so the information is not available to the coach. He is then going to review each student based on their try-out performance, but also their grade performance to determine whether they should be selected.

    In both instances, I’m evaluating the same rule but the triggers are different: I’ve got two different determination points, but I still need to understand the circumstances that give rise to those determination points. In that respect it doesn’t feel like this is truly ‘continuous’ evaluation: it feels like a reaction to a given stimulus.

    In both these scenarios, I could choose to include instances of this rule in a decision table, but I’d be trying to reach two different conclusions corresponding to the needs of the stakeholder, so it would be two different decision tables. My policy is still a verbal, structured statement, but my enforcement could use that rule as a condition in coming to a particular conclusion through a decision, whether that decision is part of a process, a case, or some other event-driven scenario.

    I’d say at this point that I’m not trying to make the case for ‘have everything as a decision’; what I’m trying to get to the bottom of is the clear distinction between the use cases for the two types of rule definition – maybe I need to read more of your literature! Ultimately, I’ve been using natural language rule expression far longer than I’ve been doing decision modelling.

    The reason understanding this distinction is important to me is that I’ve seen organisations make a real mess of enforcing behavioural rules, because they have misinterpreted how to identify the determination points. So they’ve got the rule, but not the wherewithal to understand how to enforce it.

    To that end, my thinking has been that the two types of rules *can* be different sides of the same coin. I would still expect any rule I put in a decision table to be traceable back to its behavioural roots, otherwise I’ve got no starting point for my decisions in the first place. Also, with no common reference source, I wouldn’t know whether I’m including the same rule in my decision table as my fellow analyst on the other side of the company! I’m also conscious that people get into a very ‘either, or’ mentality with their approach to analysis: it’s one method or the other and for those that do the first, the other is nonsense and for those that do the other, the first lot are mad. If people can understand and explain the distinct need and benefit of both, they can ensure others don’t throw one method out for the sake of believing they’ve found a panacea in the another.

    Nick

    • Ronald G. Ross

      Ronald G. Ross

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      Nick, A couple of quick replies …

      * What you call “determination points” (not a bad name) I call “flash points”. They are events. Treating them as decisions in any way, shape or form only causes confusion. The waters are already muddied enough as they are.

      * I can think of no good reason to use decision tables for behavioral rules or the associated flash points. Decision tables should be about … well … the logic for business decisions.

      * The distinction between behavioral rules and decision rules is clear-cut. The former is about preventing undesirable behavior; the later is about associating situations or cases with appropriate outcomes (conclusions). They are simply different beasts.

  • Han Joosten

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    Ron, It is a matter of how one looks upon the matter. (I don’t have the 4th ed, only the 1st, and I don’t have it readily at hand now). I assume you are referring to the table you also mentioned in http://www.brcommunity.com/b552.php table 1.
    As a matter of fact, the two ways of enformcement are the first two mentioned in the table. The other ones in the table are special cases of deferred enforcement, based on … Rules! (except the last one, since a guideline isn’t really a rule. It is just a guideline).

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