Rustling Up Good Definitions ~ There's a Lot Less and a Lot More to It Than You Think

Ronald G.  Ross
Ronald G. Ross Co-Founder & Principal, Business Rule Solutions, LLC , Executive Editor, Business Rules Journal and Co-Chair, Building Business Capability (BBC) Read Author Bio       || Read All Articles by Ronald G. Ross

A good definition for a business concept must be both short and long.  Fundamentally, it should focus only on the core essence of the concept -- so it should be short.  Yet specification of how the concept functions in the business -- its relevance -- is also important.  So too is knowing what constraints do and do not apply to it.  So it should to be long.  Short?  Long?  What's right?!  Let's look at some real-life examples to sort things out.

Definitions and Rule Statements

Consider the following definition created by business people concerning electrical power grid operation.

End-user:  a Party that purchases Energy to satisfy a Load directly connected to the Electric Power Grid or to a Distribution System and that does not resell the Energy

This definition says more than it needs to.  The essence of the business concept is simply "Party that purchases Energy to satisfy Load."  That is really all the definition should say.  Yet the remainder of the content is also clearly important.  What should become of that?  Here is a two-part answer.

  1. In the real world there is no obviously no way (using current know-how) for a Load to get Energy unless it is connected to the grid.  That constraint should be expressed as a separate rule, as follows.

    Rule:  The Load for which an End-User purchases Energy is always directly connected to the Electric Power Grid or to a Distribution System.

  2. What about reselling Energy?  This business actually has another term (Load-Serving Entity) for Parties that do re-sell Energy.  Consequently, we can extract the following rule from the original definition.

    Rule:  An End-user never resells purchased Energy.

Note that this constraint eliminates possibilities.  Under this rule, for example, an End-User could never be a landlord that charges tenants for the electricity they use -- precisely the case in this business.  The rule so indicates, and is therefore a valid discriminating characteristic of End-User.

Representing the two constraints above as separate rules has important advantages.

  • Business people can focus on the essence of concepts, rather than on real-world constraints.
  • An appropriate syntax (e.g., RuleSpeak®) can be used to express the rules improving their precision and consistency.
  • The constraints can participate more directly in mechanistic analysis (e.g., for discovery of anomalies).

All too often in real-life business vocabularies, we see long, jumbled definitions, in which the embedded logic is unparsable for machines (and sometimes even for people).  Definitions should be short, concise, and clear.  'Extra' semantics can be handled as rules.

Definitions and Clarification Statements

Another important opportunity related to definitions is illustrated by a second example also created by business people concerning electrical power grid operation.

Capacity:  the physical ability of a Network Component to generate or transmit Power

From this definition, one might assume (wrongly) that all Network Components either generate or transmit Power.  How is this important bit of definition-related knowledge to be expressed?  Clearly, it is not something you would want to embed in the definition.  Instead, it can be expressed as clarification.

Clarification:  A Network Component does not always generate or transmit Power.

From a business perspective, clarifications are useful for several crucial reasons. Remember that large-scale business rule initiatives involve many different people over long periods of time.

  • To officially recognize that the issue has been discussed and resolved -- that is, that there is actually no constraint
  • To make such knowledge explicit so it can be verified (hopefully, in mechanistic fashion).
  • To provide guidance to people outside the initiative, perhaps ones not even very familiar with the business.

Definitions, Rules, and Clarifications

We now have two senses of 'definition' -- the small, specific sense (the core essence), and the large, aggregate sense (a definition and all related rules and clarifications).  Does this open up a new can of worms?

Definitions picked at random from the dictionary certainly do not indicate separate rules and clarifications.  For example, consider Webster's definition of the word 'maverick.'

maverick:  unbranded range animal, esp. a motherless calf

It is important to put this definition into proper perspective.

  • It was created by definition professionals, not by business people.  So we would certainly hope it would be a well-formed one!
  • It was not created to run an actual ranching-and-cow business, to specify business rules or business strategy related thereto, or to encode any associated knowledge.  Real-life business rule initiatives, of course, must attend comprehensively to all these needs.
  • It depends on the definitions of other terms ('branded,' 'range,' and perhaps 'animal') undoubtedly also defined by Webster's.  So the 'essence' of its semantics is complete in that aggregate sense.

The definition does, however, add this interesting bit:  "esp. a motherless calf."  What is that, and how should it be represented?  Bundled into the definition?  In a real-life business, we need to provide a more direct means to capture it, which we can do in a clarification.

Clarification:  A maverick is usually a motherless calf.

To take the example further, we must go beyond the point where the dictionary leaves off.  For example, why would the ranching-and-cow business be interested in the notion of mavericks.  We can state the probable reason as a rule:

Rule:  A maverick is always considered a prime target for rustlers.

Note that piece of knowledge is not within the essence of 'maverick.'  It should not be embedded in the definition.  Nonetheless, it is obviously still important guidance.

A Definition Should Just Be a Definition

When business people form definitions, they tend to put way too much into them, especially concerning business function and/or constraints.  The rustler rule above is an example of business function -- in other words, why mavericks are relevant to the business.  That should clearly not go into the definition.

An example of a constraint is the following.

Rule:  An unbranded calf less than two months old with a living, branded mother in close proximity is never considered a maverick.

Although a discriminating characteristic for maverick, this constraint should not go into the definition either.  Note, however, the significant business knowledge this rule reflects:  (a) Branding a calf less than two months old tends to cause fatal infections (and therefore economic loss).  (b) Rustlers know a calf still so dependent on its mother is unlikely to survive on its own, so it is not worth rustling.

A Final Question

I believe most business people would consider the last two sample statements to be rules.  Are they business rules?  The case is actually not an open-and-shut one.  Clearly, the rules do provide important guidance and do underlie business strategy.  That is what business rules are all about, right?  However, they do not directly address the business aim of preventing rustling.  Is that an important distinction?  I will get to the long and the short of that important question in a future column.

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Standard citation for this article:

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Ronald G. Ross, "Rustling Up Good Definitions ~ There's a Lot Less and a Lot More to It Than You Think" Business Rules Journal, Vol. 5, No. 11, (Nov. 2004)

About our Contributor:

Ronald  G. Ross
Ronald G. Ross Co-Founder & Principal, Business Rule Solutions, LLC , Executive Editor, Business Rules Journal and Co-Chair, Building Business Capability (BBC)

Ronald G. Ross is Principal and Co-Founder of Business Rule Solutions, LLC, where he actively develops and applies the BRS Methodology including RuleSpeak®, DecisionSpeak and TableSpeak.

Ron is recognized internationally as the "father of business rules." He is the author of ten professional books including the groundbreaking first book on business rules The Business Rule Book in 1994. His newest are:

Ron serves as Executive Editor of and its flagship publication, Business Rules Journal. He is a sought-after speaker at conferences world-wide. More than 50,000 people have heard him speak; many more have attended his seminars and read his books.

Ron has served as Chair of the annual International Business Rules & Decisions Forum conference since 1997, now part of the Building Business Capability (BBC) conference where he serves as Co-Chair. He was a charter member of the Business Rules Group (BRG) in the 1980s, and an editor of its Business Motivation Model (BMM) standard and the Business Rules Manifesto. He is active in OMG standards development, with core involvement in SBVR.

Ron holds a BA from Rice University and an MS in information science from Illinois Institute of Technology. Find Ron's blog on For more information about Ron visit Tweets: @Ronald_G_Ross

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