Emergence

According to (Checkland 1999, p. 314), emergence is “the principle that entities exhibit properties which are meaningful only when attributed to the whole, not to its parts.” Questions that arise from this definition include: What kinds of systems exhibit emergence? Under what conditions do they exhibit emergence? Are emergent properties predictable? Can emergent properties be planned? How does one achieve a planned emergent property? There are many varied and even conflicting views on emergence. This article presents what is believed to be the prevailing view. Some references for other views are also provided.

Overview of Emergence

According to (Hitchins 2007, p. 7) emergence is common in nature. The emergent property “self-awareness” results from the combined effect of the interconnected and interacting neurons that make up the brain. The pungent gas ammonia results from the combination of two odorless gases, hydrogen and nitrogen.

Hitchins also notes that technological systems can also exhibit emergence. For example, the performance of a radar system results from the action of all of its subsystems. Thus, emergence always occurs at the highest level of the system hierarchy. However, he points out that to the extent that the subsystems themselves can be considered systems, they also exhibit emergence. (Page 2009) also refers to emergence as a “macro-level property.”

According to (Hitchins 2007, p. 27), emergence depends on the concept of holism that holds that “an open system is a whole” and that “the whole is different from, and may be greater than, the sum of its parts. (Page 2009) says that emergence “refers to the spontaneous creation of order and functionality from the bottom up.” (Checkland 1999) points out that the concept of holism is counter the idea of reductionism in which a system is built up from its parts.

(Bedau and Humphreys 2008) provide a comprehensive description of the philosophical and scientific background of emergence.

Emergent Properties

emergent properties are the resulting properties of emergence. Emergent properties may or may not be quantifiable. For complex systems they are generally not quantifiable. Typical emergent properties are agility and resilience . Emergent properties may or may not be predictable as discussed below. In general, emergent properties of ordered systems are predictable, while those of complex systems are not.

Types of Emergence

According to (Page 2009) there are three types of emergence, two of which are complex, while the other is called “simple emergence.”

Simple Emergence

According to (Page 2009), simple emergence is the only type of emergence that can be predicted. Simple emergence occurs in non-complex systems (see Complexity). (Sheard and Mostashari 2008) refer to such systems as “ordered.” (Page 2009) refers to non-complex systems as “equilibrium” systems. For example, the physics of aircraft flight is well-known. To achieve the emergent property of “controlled flight”, all parts of the aircraft need to be considered. It cannot be achieved alone by considering only the wings or just the control system or the propulsion system. All three (plus other elements) must be considered.

Weak Emergence

According to (Page 2009), weak emergence is emergence which is expected and presumably desired. However, since weak emergence is a product of a complex system, the actual level of emergence cannot be predicted. So how is the desired level of emergence achieved? According to (Jackson et al. 2010), the desired level of emergence can only be achieved by iteration. That is, the different design parameters of the system must be adjusted until the desired level of emergence is achieved. This can be accomplished through simulation or testing.

Strong Emergence

According to (Page 2009), strong emergence is unexpected emergence. That is, emergence is not observed until the system is simulated or tested. Strong emergence may be evident in failures or shutdowns. For example, the US-Canada Blackout of 2003 as described by (US-Canada Power System Outage Task Force, 2004) was a case of cascading shutdown that resulted from the design of the system; however, there were no equipment failures. The shutdown was completely Systemic (glossary). As (Hitchins 2007, p. 15) points out, this example shows that emergent properties are not always beneficial.

A type of system particularly subject to strong emergence is the system of systems (sos) . The reason for this is that the SoS, by definition, resulted from different systems that were designed to operate independently. When these systems are operated together, the interaction among the parts of the system results in unexpected emergence.

Other Theories on Emergence

Most sources, for example, (Hitchins 2007, p. 7), state that emergence occurs at the highest level of the system architecture. Another theory advanced by (Ryan 2007) contends that emergence is coupled to scope rather than system hierarchical levels. In Ryan’s terms, scope has to do with spatial dimensions rather than hierarchical levels.

(Abbott 2006) does not disagree with the general definition of emergence as discussed above. However, he takes issue with the notion that emergence operates outside the bounds of classical physics. He says that “such higher-level entities…can always be reduced to primitive physical forces.”

Practical Considerations

The requirement to iterate the design to achieve desired emergence, as discussed above, results in a design process that is itself more lengthy than one needed to design an “ordered” system. Hence, the vee model cannot be executed in a single direction. Repeated iterations of the model are required. The result is that complex systems may be more costly and time-consuming to develop.

Application to Enterprise Systems

Enterprise systems exhibit emergence because these systems contain humans and are therefore complex. Enterprise systems will most likely exhibit weak and strong emergence, but it is unlikely that enterprises systems will exhibit simple emergence. (Sillitto, 2008) discusses the application of the concept of emergent to “ultra large systems,” which is essentially the same as an enterprise system. Sillitto provides practical advice on how to define such a system with emergence as a consideration.

Application to Product Systems

Product systems can be either ordered or complex. Complex product systems will exhibit both weak and strong emergence. Ordered product systems will exhibit simple emergence. Application to Service Systems Like enterprise systems, service systems will exhibit weak and strong emergence. It is unlikely that a service system will exhibit simple emergence.

References

Citations

Abbott, R. 2006. Emergence Explained: Getting Epiphenomena to Do Real Work. Complexity, 12.

Bedau, M. A. & Humphreys, P. (eds.) 2008. Emergence: Contemporary Readings in Philosophy and Science, Cambridge, MA: The MIT Press.

Checkland, P. 1999. Systems Thinking, Systems Practice, New York, John Wiley & Sons.

Hitchins, D. 2007. Systems Engineering: A 21st Century Systems Methodology, Hoboken, NJ, John Wiley & Sons.

Jackson, S., Hitchins, D. & Eisner, H. 2010. What is the Systems Approach? INCOSE Insight. International Council on Systems Engineering.

Page, S. E. 2009. Understanding Complexity. The Great Courses. Chantilly, VA, USA: The Teaching Company.

Ryan, A. 2007. Emergence is coupled to scope, not level. Nonlinear Sciences.

Sheard, S. A. & Mostashari, A. 2008. Principles of Complex Systems for Systems Engineering. Systems Engineering, 12, 295-311.

Sillittoo, H. G. 2008. Design Principles for Ultra-Large-scale Systems. Second International Workshop on Ultra Large Scale Software Intensive Systems. Leipzig, Germany.

US-Canada Power System Outage Task Force 2004. Final Report on the August 14, 2003 Blackout in the United States and Canada: Causes and Recommendations. Washington-Ottawa.

Primary References

Hitchins, D. 2007. Systems Engineering: A 21st Century Systems Methodology. Hoboken, NJ, USA: John Wiley & Sons.

Page, S. E. 2009. Understanding Complexity. The Great Courses. Chantilly, VA, USA: The Teaching Company.

Additional References and Readings

Abbott, R. 2006. Emergence Explained: Getting Epiphenomena to Do Real Work. Complexity, 12.

Bedau, M. A. & Humphreys, P. (eds.) 2008. Emergence: Contemporary Readings in Philosophy and Science, Cambridge, MA: The MIT Press.

Jackson, S., Hitchins, D. & Eisner, H. 2010. What is the Systems Approach? INCOSE Insight. International Council on Systems Engineering.

Ryan, A. 2007. Emergence is coupled to scope, not level. Nonlinear Sciences.

Sheard, S. A. & Mostashari, A. 2008. Principles of Complex Systems for Systems Engineering. Systems Engineering, 12, 295-311.

Sillitto, H. G. 2010. Design Principles for Ultra-Large-scale Systems.

US-Canada Power System Outage Task Force 2004. Final Report on the August 14, 2003 Blackout in the United States and Canada: Causes and Recommendations. Washington-Ottawa