## 4 Discussion
As for VSM, BPMN2.0 is found to be complementary, because VSM is more concerned with the flow of material and information, rather than the exact sequence of activities. The more important advantage of BPMN is that it includes an execution semantic. IDEF and VSM are adequate analysis and improvement notations, but BPMN can be used to enact processes with a BPMS. [PERSON] and [PERSON] [83] also compared BPMN to other notations, but rather as the foundation for the formal specification framework of manufacturing execution systems (MES). BPMN compared favourably to flowcharts, petri-nets, Unified Modeling Language (UML) and Systems Modelling Language (SysML) This effort resulted in extensive modification of BPMN, to cater for the specific requirements of the considered cases. Similarly, [PERSON] et al. [84] present BPMN extensions for manufacturing processes, but these are again specific to the single case study. BPMN is clearly a candidate for manufacturing process modelling and enactment. It has been considered from various perspectives, including as the formal execution semantic for an MES and as a modern replacement for IDEF3. However, these considerations are somewhat ad-hoc and disparate. This research shows direct evidence for the use of BPMN for manufacturing by using a BPMS to orchestrate the execution of manufacturing processes supported by smart technologies. Furthermore, the open and standardized nature of BPMN brings additional benefit. By using international standards and open-source software, the process management system is extendible and adaptable. Companies can change the system to suit their needs or opt for a different system with the same notation. Additionally, adopting an international standard notation brings substantial embedded knowledge. BPMN enjoys extensive academic and commercial support and interest, which will see it evolve and improve over time. This status is particularly beneficial for recruitment purposes. The pool of professionals or consultants with BPMN knowledge and skill is larger than any proprietary notation. Lastly, a shortcoming of the current HORSE System realization is its interaction with other information systems. The HORSE Project team considered integration with common enterprise information systems such as enterprise resource systems (ERP) and manufacturing execution systems (MES). However, to keep the development confined to the integration of emerging technologies, the HORSE System was designed and implemented without (automated) interfaces to other information systems. This is considered as future work, because it is not expected that a system akin to the HORSE System can be implemented in isolation. In fact, it is quite possible that the principles embedded in the HORSE system architecture will be absorbed into other information systems. The process management portion of the system is a prime example. It is acknowledged that process management is a core component of many MESs. The HORSE System is not expected to replace MES, but rather show how BPM knowledge and technology can enhance or complement a conventional MES. It is not difficult to contemplate how processes are initiated in the process management system in response to scheduled triggers in the MES. Apart from the expected benefits gleaned from the practical demonstrations, the project team also encountered and overcame several challenges. The following lessons are noted:  
* Variability in a process represents a technological challenge, but it also complicates the implementation. For example, augmented reality software must be loaded with the visual information to generate the images;
* Surprisingly, the digital delivery of information represented a revolution for some factory personnel, regardless of the other benefits of smart manufacturing;
* BPMN, as the modelling notation, can be unintuitive for factory personnel. The notation does not have specific symbols for common manufacturing concepts, such as queues and staging.