Legacy Systems -- Poorly Engineered or Over-Engineered? New Insights about Business Rules and Enterprise Decisioning

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

To be honest, I have always thought about legacy systems as being poorly engineered.  I mean we know them to be unwieldy, expensive to maintain, and all-too-often unfriendly to the business.  In that sense, yes, you could say they are poorly engineered.  But that's a bit unsatisfying.  After all, most IT developers I've known are pretty astute, hard-working professionals.

In their new book, Smart (Enough) Systems,[1] Neil Raden and James Taylor offer a different point of view.  They argue that legacy systems haven't been poorly engineered, they've been over-engineered.  To say the least, that's counter-intuitive.  But I think it's probably right.  What happens when you over-engineer something?  The solution you produce is usually too stiff or rigid or cumbersome for the real-world problem.  Think tree that doesn't bend with the wind.

That's exactly the problem with legacy systems.  The speed of business itself is accelerating rapidly, but the architecture of traditional systems is rigid and static.  Raden and Taylor describe the situation (p. 113) as follows. 

Part of the problem comes from a mind-set that systems, like other enterprise assets, should be built to last.  This focus results in detailed but largely static requirements and huge investments in system architecture and design.  However, it also buries critical code in complex systems.  To make applications robust and complete, a huge amount of business expertise must be embedded in the system….

That's exactly where the problem lies -- the embedding of business expertise (read business rules) within the system itself.  Building that way is actually quite hard.  Indeed, traditional development methodologies require IT developers to have a high level of expertise both in the business and in how to implement functional requirements under the given platform(s) or language(s) most effectively.  That's a lot to ask.  Even if you get the business rules right (doubtful in itself), the rules are now hard-coded in the application logic where they are hard to find, hard to understand, and even harder to change. 

And that's just it -- the business rules will change.  So you will be revisiting the code. 

There's a certain mindset in traditional IT departments that revisiting code with any frequency means the code must be fundamentally flawed.  But with respect to business rules, that's way off-target.  Raden and Taylor say (p. 113):

An important difference in automating decisions is that, unlike other aspects of information systems, decisions change continually.  Most IT departments consider code that must be constantly revisited to be suspect or "broken" in some way.  Decisions, however, aren't static.  The best way to make a decision should be expected to change.  Organizations learn, new data is collected, and regulations change, and all these events change how you should make a decision.

The obvious solution is a separation of concerns.  Quite simply, the business rules should be engineered separately from the functional requirements.  Can you really do that cleanly and effectively?  Hello!!  That's already been proven using off-the-shelf rule engines over the last decade.  If you are coming to the Business Rules Forum Conferences this month, you'll hear from some 50 companies about how they did exactly that.

Over-engineering resulting in rigidity is not a good thing.  It results in buildings that tumble in earthquakes and bridges that collapse in windstorms.  In IT terms, it produces a world where some 75% or more of all IT resources go toward system 'maintenance'.  It's time to move on to the next engineering paradigm.  Raden and Taylor call it Enterprise Decision Management (EDM), the way to build systems smarter.


[1] Neil Raden and James Taylor, Smart (Enough) Systems: How to Deliver Competitive Advantage by Automating Hidden Decisions, Prentice-Hall (June 2007), ISBN:  0132347962.return to article

For more information on EDM and related ideas by the authors of Smart (Enough) Systems, access free recent webinars at:

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Standard citation for this article:

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Ronald G. Ross, "Legacy Systems -- Poorly Engineered or Over-Engineered? New Insights about Business Rules and Enterprise Decisioning" Business Rules Journal, Vol. 8, No. 10, (Oct. 2007)
URL: http://www.brcommunity.com/a2007/b370.html

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 BRCommunity.com 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 http://www.brsolutions.com/category/blog/. For more information about Ron visit www.RonRoss.info. Tweets: @Ronald_G_Ross

Read All Articles by Ronald G. Ross

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