## 6 Discussion
### Benefits, Limitations and Future Work
The process anomaly detection method (autorefsecdetectionUnrecognizedFailure) and the global reconfiguration method (autorefsubsec:globalReconfiguration) both have the benefit that they can be integrated in an existing fleet of AGVs, as long as the AGVs can communicate with each other and to additional infrastructure (namely, a required Digital Twin and a monitoring component). Both methods do not require complete insights into other factory components. Instead, they rely on predictions of behavioral aspects of their context that can be derived from observations made by the AGV. It is particularly beneficial if the fleet does not have access to restricted sensitive production data such as machine configurations or detailed production schedules. As a downside for the application of both methods, it is a challenge to provide a Digital Twin of the fleet of AGVs, in which the context is reflected by predictions. In [59], it is shown that the prediction of transport tasks can be performed, e.g., with random forest methods. The construction and validation of a realistic Digital Twin is out of the scope of this study. The global reconfiguration method assumes additionally that the AGVs can select between already implemented configurations (e.g., determining how the transport tasks are distributed among the fleet). The same configurations need to be implemented in the Digital Twin. In general, reconfiguration methodologies are focused to prevent factory architectures on restricting performance due to, i.e., changed factory goals, misbehaving systems etc. It is most likely sufficient to adapt system fleets to compensate for a change in the factory environment. However, the efficiency of a fleet depends on every individual system. In case of a failure of an individual AGV, usually a reconfiguration would exclude the failed system in the first place. Thus, the fleet has to assume all jobs of the excluded AGV and also needs to perform more jobs over the whole downtime, which leads to an increased workload for all remaining AGVs in the fleet. Therefore, a service-oriented reconfiguration (Section 5.2.1) can react locally at the individual AGV architecture by reconnecting service interfaces across system boundaries. Nevertheless, the use of SoR is not limited to preventing system downtime due to failed services; even more, it has the ability to extend the abilities of an individual system [51]. For future integration, SoR has to be extended by two essential functions. (1) The integration of an efficient service selection method. By using SoR in a fleet of only two systems, the number of available services is predictable, especially if both systems are equally constructed. When integrating more systems, it is easy to notice that the number of services will also increase, which on the one hand has to be included in the configuration selection process and on the other hand will increase the time to reconfigure the system. (2) Integrating an optimization algorithm is mandatory to not only replace services of the same type but even more to extend the AGV abilities and thus increase the performance and safety of each AGV. The tailored application of the Cyber Kill Chain provides a global view on possible threat scenarios against AGVs and shows opportunities for disrupting cyber-attacks in each of their phases. In addition, the results are non-exhaustive and can be enriched with further threats and mitigations in case of different or more specific use-cases. However, implementing the suggested security measures is limited by the availability of capable security tools dedicated to AGVs. Furthermore, the proposed automation, monitoring and response activities are highly dependent on the budget and skill-set of a company and will likely be out of reach for most small and medium-sized enterprises (SMEs) working with AGVs. Even with the proper budget, skills and tools, security always comprises a significant operational human aspect that co-determines the effectiveness of any technical measure.