Types of Systems

Classification methods for systems have been proposed over the past forty years, yet no standard classification system exists. Various methods that have been proposed are summarized in this article.

Classification Methods

Kenneth Boulding, one of the founding fathers of general system theory , developed a systems classification which has been the starting point for much of the subsequent work. (Boulding 1956). He classifies systems into 9 types: 1. Structures (Bridges); 2. Clock works (Solar system); Controls (Thermostat); 4. Open (Biological cells); 5. Lower organisms (Plants); 6. Animals (Birds); 7. Man (Humans); 8. Social (Families); and 9. Transcendental (God). This approach also highlights some of the subsequent issues of classification. Boulding implies that physical structures are closed and natural or social ones are open. He also separates humans from animals. (Hitchins 2007).

Peter Checkland proposed a classification system described below. (Checkland 1999) Arthur Paul surveyed the work to date and proposed methods for classifying systems. (Paul 1998) One of the most recent work was performed by Magee and de Weck, who developed a classification approach for complex systems and focused on engineered systems. (Magee and de Weck 2004) All of these classification approaches separate human-designed from non-human-designed systems or natural from man-made systems. While they provide some methods for classifying natural systems, their primary emphasis and value to the practicing systems engineer is in their classification method for human-designed or manmade systems. Peter Checkland divided systems into five classes: natural systems, designed physical systems, designed abstract systems, human activity systems and transcendental systems. The first two classes are self explanatory.

• Designed abstract systems – These systems do not contain any physical artifacts but are designed by humans to serve some explanatory purpose.

• Human activity systems (glossary) – These systems are observable in the world of innumerable sets of human activities that are more or less consciously ordered in wholes as a result of some underlying purpose or mission. At one extreme is a system consisting of a human wielding a hammer. At the other extreme lies international political systems.

• Transcendental systems – These systems that go beyond the aforementioned four systems classes, systems beyond knowledge.

Checkland refers to these five systems as comprising a “systems map of the universe”. (Checkland 1999, p.111)

Checkland, himself starting from a systems engineering perspective, successively observed the problems in applying a systems engineering approach to the more fuzzy, ill-defined problems found in the social and political arenas. (Checkland 1999, p. A9) Thus he introduced a distinction between hard systems and soft systems:

• hard systems of the world are characterized by the ability to define purpose, goals, and missions that can be addressed via engineering methodologies in attempting to, in some sense, “optimize” a solution.

• soft systems of the world are characterized by extremely complex, problematical, and often mysterious phenomena for which concrete goals cannot be established and which require learning in order to make improvement. Such systems are not limited to the social and political arenas and also exist within and amongst enterprises where complex, often ill-defined patterns of behavior are observed that are limiting the enterprise's ability to improve. Historically, the systems engineering discipline was primarily aimed at developing, modifying or supporting hard systems. More recently, the systems engineering discipline has expanded to address software systems as well.

Arthur Paul surveys previously defined classification methods and arrives at five definitions of system types based on function and usage of the systems. (Paul 1998) He defines: personal/household, military, civil, industrial and infrastructure systems as the five types of operating systems.

Magee and de Weck examine many possible methods that include: degree of complexity, branch of the economy that produced the system, realm of existence (physical or in thought), boundary, origin, time dependence, system states, human involvement / system control, human wants, ownership and functional type. They conclude by proposing a functional classification method that sorts systems by their process: transform, transport, store, exchange, or control and by the entity that they operate on: matter, energy, information and value.

Other categorizations of system types can be found throughout the literature. The varieties of suggested types that relate to specific presentations of various authors include:

• Eric Aslaksen describes three main classes of systems, according to the actions they perform: transport systems (translations in space), storage systems (translations in time), and production systems (time and space independent transformations). (Aslaksen 1996)
• Ben Blanchard describes several types including human-made systems, physical systems, conceptual systems, static systems, closed systems and open systems. (Blanchard 2005)
• Ronald Giachetti describes enterprise systems. (Giachetti 2009)
• Scott Jackson describes technological (or product) systems, product-centered infrastructure systems, technological system with human interface, human-intensive systems, process systems, socio-ecological systems, complex adaptive systems and infrastructure systems. (Jackson 2010)
• Mark Maier describes builder-architected systems, form-first systems, politico-technical systems and socio-technical systems. (Maier 2009)
• Charles Wasson describes cultural systems, business systems, educational systems, financial systems, government systems, medical systems and transportation systems. (Wasson 2006)

System Classifications

As explained in Types of Systems, the SEBoK focuses on engineered systems rather than natural or Social Systems. Engineered systems are further divided into product systems , service systems , and enterprise systems .

References

Works Cited

Aslaksen, E.W. 1996. The Changing Nature of Engineering. New York, NY, USA: McGraw-Hill.

Blanchard, B.S., and W.J. Fabrycky. 2005. Systems Engineering and Analysis, 4th ed. Prentice-Hall International Series in Industrial and Systems Engineering. Englewood Cliffs, NJ, USA: Prentice-Hall.

Checkland, P.B. 1999. Systems Thinking, Systems Practice. Chichester, UK: John Wiley & Sons Ltd.

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

Giachetti, R.E. 2009. Design of Enterprise Systems: Theory, Architectures, and Methods. Boca Raton, FL, USA: CRC Press.

Magee, C. L., O.L. de Weck. 2004. "Complex System Classification." Proceedings of the 14th Annual International Council on Systems Engineering International Symposium, 20-24 June 2004, Toulouse, France.

Maier, M., and E. Rechtin. 2009. The Art of Systems Architecting, 3rd Ed.. Boca Raton, FL, USA: CRC Press.

Paul, A. S. 1998. "Classifying Systems." Proceedings of The Eighth Annual International Council on Systems Engineering International Symposium, 26-30 July, 1998, Vancouver, BC, Canada.

Wasson, C. S. 2006. System Analysis, Design and Development. Hoboken, NJ, USA: John Wiley and Sons.

Primary References

Checkland, P. B. 1999. Systems Thinking, Systems Practice. Chichester, UK: John Wiley & Sons.

Magee, C. L., O.L. de Weck. 2004. "Complex System Classification." Proceedings of the 14th Annual International Council on Systems Engineering International Symposium, 20-24 June 2004, Toulouse, France.

Paul, A. S. 1998. "Classifying Systems." Proceedings of the Eighth Annual International Council on Systems Engineering International Symposium, 26-30 July 1998, Vancouver, BC, Canada.

Additional References

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