Having discussed opportunities and capabilities provided by CPS in the previous posting, it is natural to turn to challenges posed by CPS. There is a clear duality between opportunities and challenges, often mirroring different perspectives that relate to the same CPS capability. Take for example connectivity, providing opportunities for gathering operational data, enabling collaboration etc. while at the same time raising new security threats, failure modes and trust issues (can I trust data from another system?).

Trends towards connectivity, new services, automation, smartness, etc. imply that we are embarking towards Cyber-Physical Systems of Systems (CPSoS), for example in terms of intelligent transportation systems composed of collaborating (semi-) autonomous vehicle, infrastructure and various traffic management services. The CPSoS will be formed by dynamically integrating systems developed by multiple providers, acting in highly changing environments.

On a societal scale, infrastructures for e.g. water, energy, transportation, etc. will be relying on the services provided by multiple CPS. Unless such infrastructures are properly developed and maintained, the society will be vulnerable if these services are not available or malfunction. It is thus evident that special care needs to be devoted towards the entire life-cycle of these CPS; we want them to be trustworthy. The development of future CPS raises a host of related challenges including the following:

• Ensuring safety, security and availability at affordable cost. A key issue here is that of managing the complexity of future CPS (I will return to this topic in a forthcoming posting).
• Providing CPS which are understandable and intuitive, working well with humans!
• Setting the requirements for future CPS. Since these systems are likely to change our behaviors, and since they are new, this is not an easy task (compare for instance with autonomous driving where standards and legislation are lagging technological developments). The introduction of future CPS thus interplays with (evolving) regulations, standards and public expectations.
• Designing future CPSoS, in terms of regulations, rules, and coordination protocols that define proper interactions among individual CPS. This will be very difficult because of technical complexity and because multiple organizations are involved in open markets. I will however be very important to pursue this in order to avoid large scale risks, e.g. caused by unforeseen and unintended feature interactions.
• Ensuring robustness and safety of AI technologies that are likely to be increasingly adopted as part of CPS.
• Dealing with sustainability of the CPS themselves, i.e. ensuring that all the electronics dispersed into our societies can be dealt with as part of a circular economy.

The drivers for, and capabilities of CPS, has the implication and downside that future CPS will be of unprecedented complexity. There is strong need for new theory, methods and tools for countering and managing this complexity. To pursue this, collaborative and multidisciplinary efforts will be important; the CPS challenges go beyond what single disciplines have to offer.