A review of ISO/IEC/IEEE/DIS 21840 Systems and software engineering – Guidelines for the utilization of ISO/IEC/IEEE 15288 in the context of System of Systems (SoS) engineering

This post reviews ISO/IEC/IEEE/DIS 21840 Systems and software engineering – Guidelines for the utilization of ISO/IEC/IEEE 15288 (NEN-ISO/IEC/IEEE 15288, 2015) in the context of System of Systems (SoS) engineering. A draft of this document is circulated for comments and approval. The document is therefore yet subject to change and might not yet be referred to as an international standard until published as such[1]. While (NEN-ISO/IEC/IEEE 15288, 2015) applies to systems (including constituent systems), this document provides guidance on the application of these processes to SoS. The scope of the (draft) standard is the same as (NEN-ISO/IEC/IEEE 15288, 2015), which establishes a common framework of process descriptions for describing the life cycle of systems created by humans.  It defines a set of processes and associated terminology from an engineering viewpoint.  These processes can be applied at any level in the hierarchy of a system’s structure.  Selected sets of these processes can be applied throughout the life cycle for managing and performing the stages of a system’s life cycle.  This is accomplished through the involvement of all stakeholders, with the ultimate goal of achieving customer satisfaction, hence addresses more than system engineering activities. In addition it explores the similarities and differences between systems and SoS and, by extension, the similarities and differences between engineering of systems and SoS.

System of systems engineering (SoSE) is not a new discipline; however, this is an opportunity for the systems engineering community to define complex systems of the twenty-first century (Jamshidi, 2008). While systems engineering is a fairly established field, SoSE represents a challenge for the present system engineers on global level. In general, SoSE requires considerations beyond those usually associated with engineering to include socio-technical and sometimes socio-economic phenomena (SEBoK, 2018). Moreover, according to (NEN-ISO/IEC/IEEE 15288, 2015): “an SoS brings together a set of systems for a task that none of the systems can accomplish on its own. Each constituent system keeps its own management, goals, and resources while coordinating within the SoS and adapting to meet SoS goals.” It is noticeable that based on this definition, formation of an SoS is not necessarily a permanent phenomenon, but rather a necessity for integrating and networking systems in a coordinated way for specific goals such as robustness, cost, efficiency etc. An SoS may also be defined to accommodate varying missions, some of which cannot yet be defined with any precision (Madni & Sievers, 2014). Nevertheless, application of systems engineering to system of systems has become increasingly important for the realization and sustainability of large and persistent socio-technical systems (ISO/IEC/IEEE DIS 21840, 2019).  This results in a wide variety of ways in which SoS are developed and operate, from centrally controlled ones to those with very little control at all. Depending on the nature of the SoS, governance can be implemented in a different manner. Moreover, (Madni & Sievers, 2014) classifies SoS according to the way it is managed and its openness to change and new capabilities, ranging from virtual SoS with among others: no central management authority and no centrally agreed upon purpose, to directed SoS, where integrated SoS is built and managed to fulfil specific purposes.

The document commences with explaining the relationships to other standards, as it is part of a set of documents which are intended to be used together i.e. ISO/IEC/IEEE 15288, ISO/IEC/IEEE 21839, ISO/IEC/IEEE21840, ISO/IEC/IEEE 21841. Although this is quite understandable from the text, the graphical representation related hereto is less comprehensible. Moreover, utilization of numerous standards simultaneously could be a daunting task. Nevertheless, the document addresses various terminological databases for use in standardization, in which terms and definition are maintained and clearly stated.

Within this (draft) standard, the differences between systems and SoS, and by extension the difference between engineering of systems and SoS are clearly indicated and graphically represented. Moreover, the differences between these are adapted from distinct sources (Boardman & Sauser, 2006; Maier,1998) and range from e.g. differences in the level of autonomy to the level of emergence. Furthermore, ISO/IEC/IEEE 21841 provides a taxonomy for SoS, providing specific viewpoints that align with the management and government concerns. Using a taxonomy in conjunction with this document could facilitates better communication between various stakeholders that are involved in activities like governance, engineering, operation and management of SOS. For SoS, decisions can effect multiple constituent systems (CSs), so CS should be engaged in both the decision and analysis processes along with the SoS. This is especially true when CS are managerially independent of the SoS. Depending on the governance independence of the SoS, problem treatment as well as definition of priorities should be agreed upon between governing and managing authorities of each CS, and treated collaboratively. Based on all of the abovementioned, the document clearly indicates that collaboration is certainly required within the SoS context.

 In addition, although this (draft) standard is aimed to be a guideline for ISO/IEC/IEEE 15288, it is certainly written comprehensible, in the sense of its SoS engineering application within other fields. Moreover, as the structure of this (draft) standard is similar to that of ISO/IEC/IEEE 15288, the differences (or additions required in the case of SoS) of its application to systems in comparison to SoS are presented straightforward. In many cases however, the document states that ISO/IEC/IEEE 15288 processes or process outcomes”…applies as stated to SoS.” These areas should however be cautiously approached, because interpretation within the context of SoS is still required.

Although this (draft) standard has some strong points as just stated, it also contains some ambiguous aspects. This document provides general guidance for  application of ISO/IEC/IEEE 15288 process and process outcome in the context of SoS, but does not address specific activities, tasks, methods or procedures to do so, in addition, processes and process outcomes unique to SoS could still be needed. Additionally, a frequently occurring statement within the (draft) standard is: “depending on the degree of managerial independence, the approach….could be quite different, or additional resources would be required to support an SoS”  etc., however, related to the spectrum of SoS as previously mentioned, no distinguishment is provided whatsoever related to application of the (draft) standard.

Surely interesting within the document are the slightly contradicting additions, e.g. “For SoS, it might not be possible to identify all stakeholders, especially given that CS will continue to have managerial and operational independence as well as interdependence. However, it is important to be cognizant with the stakeholder needs which could align with the SoS objectives.” Additionally, within the (draft) standard a fairly cynical undertone was noticeable. Numerous examples can be indicated which include, but are certainly not limited to:  “documenting stakeholders is very complicated given that CS will continue to have managerial and operational independence as well as interdependence, however this does not eliminate the need for it. These should be addressed for each CS, even if the information is vague.” Alongside this, “because it might not be possible to identify all stakeholders, and their needs, prioritizing them and transforming them into requirements is likely to be incomplete.”

Although these indications might be correct, they do not necessarily provide guidelines for utilization. Nevertheless, it is stated within this (draft) standard that the guidance contained within the document is expected to evolve as the discipline matures.

Summing up, this is an overall interesting (draft) standard, providing general guidelines for the utilization of ISO/IEC/IEEE 15288 in the context of System of Systems (SoS) engineering, and indicates additions for all lifecycle processes in the case of SoS in contrast to systems. Nevertheless, does not indicate specific activities, tasks or methods. Hence, certainly exhibits room for improvement.

Boardman, J., & Sauser, B. (2006, April). System of Systems-the meaning of of. In 2006 IEEE/SMC International Conference on System of Systems Engineering (pp. 6-pp). IEEE.

ISO/IEC/IEEE. (2019). ISO/IEC/IEEE DIS 21840 Draft International standard-systems and software engineering-Guidelines for the utilization of ISO/IEC/IEEE 15288 in the context of System of Systems (SoS) engineering. New York: ISO/IEC/IEEE.

ISO/IEC/IEEE. (2015). NEN-ISO/IEC/IEEE 15288 (en)-Systems and software engineering-System life cycle processes (ISO/IEC/IEEE 15288:2015,IDT). New York: ISO/IEC/IEEE.

Jamshidi, M. (2008, December). System of systems-innovations for 21st century. In 2008 IEEE Region  10 and the Third international Conference on Industrial and Information Systems (pp. 6-7). IEEE.

Madni, A. M., & Sievers, M. (2014). System of systems integration: Key considerations and challenges. Systems Engineering, 17(3), 330-347.

Maier, M. W. (1998). Architecting principles for systems‐of‐systems. Systems Engineering: The Journal of the International Council on Systems Engineering, 1(4), 267-284.


[1] Voting of this documents terminates 26-04-2019.