## 3 VIDAF Architectural Framework
### Design Methodology  
The VIDAF provides a COTS-based framework to develop and implement reliable real-time applications. One of the key features of the design approach followed is based on the use of open-source and general-purpose hardware/software components, due to their immediate availability, rapid utilization and implementation, low-cost and wide-range of applicability. The competitive advantages of this approach in cost and time savings by using standardized readily available hardware/software components are evident. General-purpose components are more versatile and expandable over custom-built components since their functionality could also be upgraded and extended via custom development.  
The design methodology extends this approach in incorporating real-time and open-source scheduling techniques, applied in system applications in education and manufacturing. Aspects such as availability, reusability, reliability, and cost-efficiency are taken into consideration during the development, for the purposes and context of specific critical and non-critical system applications. The methodology addresses all together such issues and challenges that pose the integration of standard commercially off-the-shelf hardware and software components, into the development of an architectural framework for control systems in real-time applications. It investigates the optimal design of operational real-time scheduling techniques for systems deployed in critical applications (e.g., in manufacturing). Schedulability analysis techniques are applied to specify the real-time requirements for such systems applications deployed in real-time critical applications. The techniques and approaches within this methodology build upon recent [32; 33] and previous [34; 35] research on developing real-time embedded control systems using standardized components and equipment. In particular, a model-based and component-based design methodology [36; 37] is applied in combination with real-time multithreaded scheduling techniques [38] in analyzing the needs and requirements for building reliable systems, including the real-time performance of hardware components and software modules in control systems applications. Previous research has shown that this methodology is feasible and credible in real-time control system applications with excellent results [39]. The delivered architectural framework combinesformal verification techniques in simulation at an early prototyping stage and real-world validations, which promote innovation by facilitating the development, exploration, and implementation of such systems at reduced time and cost.  
Upon this methodology, further on, a COTS-based development process is presented, which takes into consideration specific requirements (such as the flexibility, reusability, reliability, and cost-efficiency) of hardware and software COTS components. For validation purposes, this is applied to the development of a control system architecture in a manufacturing case study. The experimental results, based on extensive experiments on the actual machine under control and documented with system-specific measurements (e.g., accuracy and timing metrics), provide evidence that the COTS-based control system performs reasonably well and correctly (compared to previous custom-build solutions). In addition, the adequate operation of the COTS-based control application demonstrates that the system infrastructure of this architectural framework enables the integration and communication of COTS hardware and software components in real-time, making applications work together as one integrated system. Overall, the outcomes reconfirm the applicability and validity of the proposed framework methodology and approach. Such experimental results could be worthy and have a positive impact on emerging areas such as Industrial IoT.