Rules as Constraints: On or By the System Design?

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

In this one-per-month special 'notepad' series, I am taking a quick look at important issues facing practitioners who are seeking to understand and apply the business rules approach for capturing business requirements and developing business systems.

Let's work the question from a set of sample rules.  These are rules that might be captured as part of a business model (Zachman row 2) -- that is, as business requirements to be supported by a system design[1] (Zachman row 3).

Rule:  A group must not include both union members and non-union members.

Rule:  A poor-risk customer must not place a rush order.

Rule:  An employee's new salary must be greater than or equal to the employee's current salary.

Rule:  A truck carrying hazardous material must not be routed through a downtown street.

Rule:  A trainee must not send a memo to a manager without permission of his supervisor.

Rule:  A person must be considered a woman, if the person is female and is over 21.

Do these rules represent constraints to be imposed 'on' the system design?  Perhaps the answer is yes in the general sense that all business requirements are 'constraints' on a system design, but the true sense of these rules is much more specific than that.  A more accurate view of rules is that they are constraints to be imposed by a system design.  In that sense, only a subset of all business requirements qualifies as 'rules.'

It is also accurate to say that rules are something to be imposed by the system at run time.  This implies some technology to impose them.  But how the system 'imposes' rules is a class-of-platform issue (Zachman row 4) because it presupposes a class-of-platform selection -- for example, a rule engine (declarative implementation) vs. Java or COBOL (procedural implementation), or workflow engine, scheduler, security package, etc.

The system design itself should not indicate how rules are to be tested/fired.  Not having to categorize or analyze rules according to class-of-platform issues proves to be hugely simplifying.  At that level, rules are simply rules -- no class-of-platform concerns necessary!


[1]  By system in this discussion, I mean a knowledge/record-keeping system to support business requirements. return to article

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Standard citation for this article:

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Ronald G. Ross, "Rules as Constraints: On or By the System Design?" Business Rules Journal, Vol. 4, No. 7, (Jul. 2003)

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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