AS/NZS ISO/IEC/IEEE 21841:2021 pdf download – Systems and software engineering — Taxonomy of systems of systems.
4  Concepts and application 4.1  Overview Taxonomies provide a means in many fields to classify and describe the relationships between the relevant elements being studied. The elements of a taxonomy, or taxa, form a partitioning or means of classification within that body of knowledge. Partitioning based on essential characteristics provides an abbreviated nomenclature to refer to a larger composite of characteristics, facilitating discussion about the partitions (taxa) without having to refer to each of the characteristics. 4.2  Importance of taxonomies to SoS In systems engineering (SE), the relevant pieces of the system of interest can be called subsystems, elements or components. In the context of SoS, the relevant pieces of the system of interest are, by definition, systems themselves. These are called constituent systems (CS) throughout this document. That is, an SoS consists of some number of CS, plus any inter-system infrastructure, facilities and processes necessary to enable the CS to integrate or interoperate. Relationships between CS affect the SoS. Using essential characteristics to partition the various types of SoS provides an abbreviated nomenclature for thinking about SoS. While Clause 5 elaborates one mature SoS taxonomy, Annex A provides a list of SoS less-mature taxonomies. Based on taxonomies, different approaches to the engineering of systems of systems are possible, improving the efficiency and effectiveness of SoSE. NOTE 1  Taxonomies can have some overlap in their definition and need not be orthogonal to each other to be useful. An SoS can be considered as belonging to several taxonomies as long as its characteristics meet the definitions of the taxonomies. NOTE 2  It is possible that inter-system infrastructure, facilities and processes do not meet the criteria for being systems in their own right. From the perspective of the SoS, these could be system elements (or SoS elements).
5  Taxonomies for systems of systems 5.1  General SoS taxonomies organize the relevant aspects or essential characteristics of SoS, providing specific viewpoints that align with stakeholder concerns. Taxonomies can have some overlap in their construction, but the lack of orthogonality does not inhibit their application. Since most of the taxonomies are not explicitly named, they are most often referenced in practice by the author’s names or the names of the taxa. Consequently, the taxonomies are presented using the taxa names themselves, using the author’s order. 5.2  Taxa: directed, acknowledged, collaborative and virtual 5.2.1  Overview In this taxonomy, SoS are classified according to the degree of managerial and operational independence. Four types are defined: directed, acknowledged, collaborative and virtual. This taxonomy is mature, originating in the work of Maier (1998) [6] , expanded by Dahmann and Baldwin (2008) [9] and published as an informative annex in ISO/IEC/IEEE 15288. Maier’s observation was that SoS are not simply systems in which the constituents are also systems. One essential characteristic is that constituent systems within the SoS are operationally independent. Operational independence means that the CS are able to usefully operate independently, that is, fulfil customer purposes on their own. Consequently, SoS deal with multiple consumers that can have different priorities and expectations. Unlike a system, which has been designed to fulfill a purpose and an expected quality of service, the quality of service within an SoS can be subject to additional variation.
Another essential characteristic is that the CS within the SoS are managerially independent. The CS operate with each other to produce the SoS capabilities; however, managerial independence means that the CS also not only can but do operate independently from each other. This suggests that the CS are managed independently, and that these organizations can have different goals and objectives for the CS. If so, the degree of independence of governance can be more appropriate than the degree of independence of management. Regardless of the means of managing the organizations, alignment (or lack thereof) in the goals and objectives affect the system of systems.