Definitions used throughout the project:
1) Systems of systems (SoS)
is a relatively new concept from the domain of systems engineering.
Maier (1) stated five key characteristics of SoS:
- Operational independence of the components of the overall system
- Managerial independence of the components of the overall system
- Geographical distribution
- Emerging behaviour
- Evolutionary development processes.
Jamshidi (2) provided a broader definition of SoS: “A SoS is an integration of a finite number of constituent systems which are independent and operable, and which are networked together for a period of time to achieve a certain higher goal.” The concept of systems of systems is understood here in this broad and pragmatic sense, comprising systems where most of the components have some managerial and operational independence, but the purpose of the system is to provide a function or service that cannot be provided by the individual systems independently, or cannot be provided in an as efficient manner as by the overall system. As an additional key characteristic, in a system of systems the structure, the connectivity and the “membership” of the components can change dynamically over time, components can be added or connected and disconnected and be dynamically reconfigured. Emerging behaviour of the global system must be considered as a possibility, but is not necessarily an intended property of the system, so by design one may want to achieve a controlled global behaviour rather than behaviour that emerges in an unforeseen manner.
An evolutionary development process is typical for SoS as for any large system that is in operation over a significant period of time. Partial autonomy of several components of a system of systems is constitutive for the concept. Autonomy in this context does not necessarily mean human‐free operation except in very specific areas; in contrast, human supervision and human interventions and utilization are usually an important element of the subsystems as well as of the overall system.
From an engineering point of view, this leads to uncertain behaviours but also to the need of making the systems transparent to the users as much as possible.
2) Systems of systems engineering (SOSE)
deals with planning, analysing, organising, and integrating the capabilities of a mix of existing and new systems into a system of systems with greater efficiency or additional capabilities compared to the constituent parts. SOSE is a developing multidiscipline, spanning across and drawing from a variety of disciplines to address complex situations characterised by ambiguity, high uncertainty and emergence.
3) Cyber‐physical systems
are systems where real‐time computing and physical systems interact tightly. This is also the case in embedded systems, and sometimes cyber‐physical systems is used as synonymous for embedded systems, with a stronger emphasis on the interaction with the physical world and on connectivity, e.g. over the internet. The German “Agenda CPS4” is an example of this view.
We here take the concept of cyber‐physical systems as meaning large complex physical systems that are interacting with a considerable number of distributed computing elements for monitoring, control and management which can exchange information between them and with human users. The elements of the physical system are connected by the exchange of material, energy, or momentum while the elements of the control and management system are connected by communication networks which sometimes impose restrictions on the exchange of information. Prototype systems are the electrical grid, a power plant, an airplane or a ship, a manufacturing process with many cooperating elements as e.g. robots, machines, warehouses, and conveyer belts, a large processing plant with many process units, a building with advanced distributed HVAC control, etc.
4) Cyber‐physical Systems of Systems
are cyber‐physical systems which exhibit the features of systems of systems:
- Large, often spatially distributed physical systems with complex dynamics
- Distributed control, supervision and management
- Partial autonomy of the subsystems
- Dynamic reconfiguration of the overall system on different time‐scales
- Possibility of emerging behaviours
- Continuous evolution of the overall system during its operation.
(1) Maier, M.W. “Architecting Principles for System of Systems,” Systems Engineering, Vol. 1, No. 4, 1998, pp. 267‐284.
(2) Systems of Systems Engineering: principle and applications. Jamshidi, M., ed., CRC Press, 2009.