Theory of Constraints Handbook - James Cox Iii [453]
However, while TOC’s definition and usage of feedback loops is unambiguous in the context of TOC, and used with consistency within the TOC community, such definition and usage are unnecessarily out of step with the rest of the systems community. We suggest that a change in process and definition should be contemplated by the TOC community. In other systems methodologies, any feedback loop that reinforces an effect is termed a “positive feedback loop.” Indeed, in most systems methodologies, both “vicious” and “virtuous cycles” are conceptualized and labeled as positive feedback loops—the simplest example being that of two variables that act on each other in a mutually reinforcing manner—with each variable causally effecting and being causally effected by the other to create greater effects of a positive or negative nature. By contrast, a negative loop is one that moderates an effect, that brings a variable back on course in the sense that it incorporates one or more cause-effect relationships that bring a system back to a desired state, like a thermostatically controlled air conditioning system. Relabeling and redefining the TOC loops accordingly would facilitate a shared understanding and acceptance of TP diagrams, and the TOC approach more generally, by other systems communities.
Exploring the link between TOC and other systems methodologies can also enhance understanding of problem situations. Indeed, we have argued elsewhere (e.g., Davies and Mabin, 2009) that each of the EC and CLD representations can be enhanced by multi-methodological use to display relationships, not only using necessity logic, but also—with appropriate explanatory intermediate variables emanating from assumptions underlying the EC—using if-then sufficiency logic. Such examples illustrate beneficial developments in TOC methods that may be sought over time to improve TOC as a methodology, and to enhance the use of particular TP tools.
Ronen’s comments (2005) also suggest that, regardless of such shortcomings, it is necessary to establish the credibility of TOC as a methodology within academia. In his early writings, Goldratt (1990b, 23) described the development of scientific theories as a progression through classification, correlation, and causation stages. Here we have provided the classificatory frameworks that form a basis for understanding how TOC TP methods and methodology within TOC are constituted.
Summary
What Has Been Covered in This Chapter
This chapter has provided an overview of the TP that has addressed their conceptual, philosophical, and methodological foundations, alongside discussion of the TP use and practice. As such, we have been able to reflect on the need for the TP; on the design and purpose of the TP; on their effective use in practice; on reasons for their existence and effectiveness; and we have done so in order to effect a consolidation of our understanding of the TP that may serve as a platform for future developments and use.
In doing so, we have provided a supporting rationale for the existence of the TP by explaining how they meet needs of a methodological and practical nature that are not addressed by other problem-structuring and problem-solving methods, for example, those of OR/MS. We have also suggested that there is a need to explore how the TP may be used in multi-method and multi-methodological intervention with, say, OR/MS or systems methods, with other TP tools, and with other TOC methods. In addition, we believe that building such links and bridges with cognate fields and disciplines through multi-methodological intervention, exploiting identified synergies, may well serve to gain further acceptance for TOC within those cognate fields, through the building of communities of practice, with, say, those embracing systems and soft OR methodologies.
Furthermore, we respond to the call for the domain of TOC practice, and for TOC as an academic field of inquiry, to gain further recognition from cognate professional groups and academia, by suggesting further engagement in research on