Types of Systems
Lead Author: Rick Adcock, Contributing Authors: Brian Wells, Scott Jackson, Gary Smith
Engineered systems are purposeful, human-made systems created to achieve specified objectives. They are the primary focus of systems engineering practice, requiring definition, design, integration, and management across their life cycles.
This article complements related entries on Natural Systems and Socio-Technical Systems. Together, these perspectives provide a balanced view of the types of systems encountered in practice: natural systems that evolve without human intervention, engineered systems designed to fulfill specific goals, and hybrid socio-technical systems that integrate people and technology.
Engineered systems can take many forms, including products, services, enterprises, and systems of systems. They exist within larger contexts, often interacting with natural environments and social organizations, and are subject to constraints such as physical laws, resource limits, and stakeholder requirements. Recognizing these contexts is essential for defining the system of interest (SoI) and ensuring that engineered solutions are sustainable, adaptable, and fit for purpose.
System Classification
Engineered systems are one class within broader taxonomies of systems developed in systems science. Several influential frameworks include:
- Boulding (1956): A hierarchical classification ranging from structures and organisms to social and transcendental systems.
- Checkland (1999): Five categories: natural systems, designed physical systems, designed abstract systems, human activity systems, and transcendental systems.
- Magee and de Weck (2004): A functional classification of systems by process (transform, transport, store, exchange, or control) and by the entity on which they operate (matter, energy, information, or value).
These classifications highlight the diversity of systems and their different purposes. Within this landscape, engineered systems are distinguished as designed physical and organizational systems, intentionally created by humans to deliver specified outcomes. They are therefore central to systems engineering, which provides the processes, principles, and heuristics for their conception, realization, operation, and evolution..
Types of Engineered System
Engineered systems can be grouped into four general contexts that are commonly recognized in systems engineering practice: product systems, service systems, enterprise systems, and systems of systems (SoS). Each represents a possible system of interest (SoI) within a life cycle.
Figure 1 illustrates these contexts. A product may exist as a technology-focused system, integrated into a service; services are delivered and sustained by enterprises; and in many cases, systems are combined to form larger systems of systems
Products and Product Systems
A product system is an engineered system focused on the creation and delivery of tangible or intangible products, such as hardware, software, or information artifacts. The life cycle of a product system typically includes design, production, operation, sustainment, and eventual retirement.
Products do not exist in isolation: they interact with people (operators, maintainers, producers) and are deployed within service systems that deliver capabilities to an enterprise or society. Effective product system engineering therefore requires attention to both the product itself and its wider context.
Services and Service Systems
A service system is an engineered system that delivers outcomes or benefits to users. Services are processes or performances co-created with clients or stakeholders. Examples include transportation, healthcare, communications, and information technology services.
Service systems are often information-intensive and software-defined. They may involve combinations of products, people, and supporting infrastructure, integrated close to the point of use. Systems engineers address both the design of the service and the management of its delivery, ensuring performance, quality, and adaptability over time.
Enterprise Systems
An enterprise system is a purposeful network of people, processes, organizations, and technologies that interact to achieve shared goals. Enterprises are unique in that they are constantly evolving, rarely have fixed requirements, and typically balance multiple objectives such as customer satisfaction, stakeholder value, and long-term sustainability.
Systems engineering supports enterprises through enterprise architecture and related modeling approaches, which describe current capabilities and plan for future ones. These tools allow enterprises to align their strategy with the product and service systems that support their operations.
Systems of Systems
A system of systems (SoS) is an arrangement of independent systems that retain operational and managerial autonomy but are integrated to provide new capabilities. Examples include national defense networks, air traffic management systems, and smart cities.
SoS engineering involves unique challenges, including governance, interoperability, and lifecycle coordination across independently managed systems. As integration technologies become more common, SoS considerations are increasingly central to modern systems engineering practice.
Applying Engineered System Contexts
In practice, real-world systems often combine aspects of product, service, enterprise, and system-of-systems contexts. A single engineering effort may involve producing new products, deploying them within services, managing them through an enterprise, and integrating them into larger federations of systems.
A key activity in systems engineering is to identify the system of interest (SoI) and clearly define its boundaries, context, and dependencies. The SoI always exists within a wider environment, which includes enabling systems, external influences, and interactions with natural and socio-technical systems. Recognizing these interdependencies is essential for ensuring that engineered systems are effective, sustainable, and adaptable throughout their life cycles.
Relationship to Other System Types
Engineered systems represent only one category of systems:
- Natural Systems, occur without human intervention, governed by physical and ecological processes. They provide both constraints and models for engineered solutions (see Natural Systems: Definition and Natural Systems: Principles and Attributes).
- Socio-Technical Systems, hybrid systems combining people, organizations, and technologies. These are particularly relevant when engineered systems are embedded in social or organizational contexts.
- Designed Abstract Systems, systems of ideas or symbols, such as taxonomies, standards, or mathematical models, which provide frameworks for organizing knowledge or guiding action.
By situating engineered systems within this broader landscape, systems engineers can better appreciate the relationships, dependencies, and shared principles that connect different kinds of systems. This holistic perspective enables integration across domains and supports the development of solutions that are both technically sound and contextually appropriate.
References
Works Cited
Boulding, K. E. (1956). “General systems theory: The skeleton of science.” Management Science, 2(3), 197–208.
Checkland, P. B. (1999). Systems Thinking, Systems Practice. Chichester, UK: John Wiley & Sons.
Magee, C. L., & de Weck, O. L. (2004). “Complex system classification.” Proceedings of the 14th Annual INCOSE International Symposium, Toulouse, France, June 2004.
Primary References
ISO/IEC/IEEE 15288:2023. Systems and Software Engineering, System Life Cycle Processes. Geneva, Switzerland: ISO/IEC.
INCOSE. (2022). INCOSE Systems Engineering Vision 2035. San Diego, CA: International Council on Systems Engineering.
Dahmann, J., Baldwin, K. J., & Goodnight, J. (2020). “Systems of Systems Engineering: Essential Concepts and Practical Examples.” INCOSE International Symposium, Cape Town, South Africa.
Additional References
Blanchard, B. S., & Fabrycky, W. J. (2010). Systems Engineering and Analysis (5th ed.). Upper Saddle River, NJ: Prentice Hall.
Maier, M., and E. Rechtin. 2009. The Art of Systems Architecting, 3rd Ed. Boca Raton, FL, USA: CRC Press.
Rebovich, G., & White, B. E. (eds.). (2011). Enterprise Systems Engineering: Advances in the Theory and Practice. Boca Raton, FL: CRC Press.