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8

Current and Future Reality Trees

Timothy Yoap

Traditional Six Sigma tools are very effective for addressing operational issues where
problems are well-defined (e.g. reducing the failure rate of a certain failure mode), key
process input and output variables are measurable, and solutions are arrived at by
reducing variation through optimization of input parameters. In the transactional and
business worlds, although there are attempts to force-fit or adapt the existing tools to
solve problems, most of the time they are either not efficient or totally ineffective. The
traditional Six Sigma toolset is often insufficient, especially in defining the problem
and exploring probable solutions. In this chapter, we present the current reality tree
and the future reality tree, two of the six thinking process tools in the theory of
constraints developed by Goldratt. These perform similar functions to traditional Six
Sigma tools. We compare the various tools and suggest how to incorporate current
and future reality trees into the Six Sigma toolset.

8.1 INTRODUCTION

The current reality tree (CRT) and future reality tree (FRT) are two of the thinking
process tools in the theory of constraints (TOC), a management philosophy devel-
oped by Eliyahu M. Goldratt. 1,2 The TOC is divided into three key interrelated areas:
performance measurement, logistic control, and logical thinking processes. Perfor-
mance measurement includes throughput, inventory, and operating expenses, and is
concerned with making sure resources are focused on the bottleneck. Logistic control
includes drum--buffer--rope scheduling and buffer management. Thinking process
tools are important in understanding the current situation and eventually identify-
ing the root problem (using the CRT), identifying and expanding win--win solutions
(using the FRT and evaporating cloud), and developing implementation plans (using
the prerequisite tree and transition tree).

Six Sigma: Advanced Tools for Black Belts and Master Black Belts L. C. Tang, T. N. Goh, H. S. Yam and T. Yoap
C 2006 John Wiley & Sons, Ltd
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