Cyber Physical Systems (CPS) bridge the cyber-world of computing and communications with the physical world and require development of secure and reliable software. It asserts a big challenge not only on testing and verifying the correctness of all physical and cyber components of such big systems, but also on integration of these components. This paper develops a categorization of multiple levels of testing required to test CPS and makes a comparison of these levels with the levels of software testing based on the V-model. It presents a detailed state-of-the-art survey on the testing approaches performed on the CPS. Further, it provides challenges in CPS testing.

The Multi-Resource Server (MRS) technique has been proposed to enable predictable execution of memory intensive real-time applications on COTS multi-core platforms. It uses resource reservation approaches in the context of CPUbandwidth and memory-bus bandwidth reservations to bound the interference between the applications running on the same core as well as between the applications running on different cores. In this paper we present a complete composable local and global schedulability analysis for the Multi-Resource Server technique. Based on the proposed analysis,we further provide an experimental study that investigates the behaviour of the MRS and identifies the factors that contribute mostly on the overall system performance.

In this paper we present challenges that hinder the predictable integration and execution of real-time applications on multicore platforms. We investigate how shared resources, like CPU, memory-bus bandwidth, caches, and memory cause unpredictability and interference. We propose to adapt the traditional server-based scheduling approach on the multicore platforms with additional resource-reservations to control the shared access to such resources and present the multi-resource server as a solution such that the execution of real-time applications becomes predictable. 

The Multi-Resource Server (MRS) technique has been proposed toenable predictable execution of memory intensive real-time applicationson COTS multi-core platforms. It uses resource reservationapproaches in the context of CPU-bandwidth and memory-busbandwidth reservations to bound the interferences between the applicationsrunning on the same core as well as between the applicationsrunning on different cores. In this paper we present a completecompositional schedulability analysis for the Multi-ResourceServer technique. Based on the proposed analysis, we further providean experimental study that investigates the behaviour of theMRS and identify the factors that contribute mostly on the overallsystem performance.

Hierarchical scheduling frameworks (HSFs) are a means for composing complex real-time embedded systems from independently developed and analyzed applications. To support multiple modes in a two-level HSF, the multi-mode adaptive hierarchical scheduling framework MMAHSF has recently been presented supporting different mode-change mechanisms. Currently, we provide a formalization and verification of mode changes in MMAHSF using the UPPAAL model checker for certain mode-change mechanisms. The verification indicates that MMAHSF and the proposed mode-change mechanisms are deadlock-free and guarantee mode changes in bounded time.

Hierarchical scheduling frameworks (HSFs) are a means for composing complex real-time embedded systems from independently developed and analyzed applications. To support multiple modes in a two-level HSF, the multi-mode adaptive hierarchical scheduling framework MMAHSF has recently been presented supporting different mode-change mechanisms. Currently, we provide a formalization and verification of mode changes in MMAHSF using the UPPAAL model checker for certain mode-change mechanisms. The verification indicates that MMAHSF and the proposed mode-change mechanisms are deadlock-free and guarantee correct mode changes in bounded time.

This dissertation presents techniques to achieve predictable execution of coarse-grained software components and for preservation of temporal properties of components during their integration and reuse.

The dissertation presents a novel concept runnable virtual node (RVN) which interaction with the environment is bounded both by a functional and a temporal interface, and the validity of its internal temporal behaviour is preserved when integrated with other components or when reused in a new environment. The realization of RVN exploits techniques for hierarchical scheduling to achieve temporal isolation, and the principles from component-based software-engineering to achieve functional isolation. The proof-of-concept case studies executed on a micro-controller demonstrate the preserving of real-time properties within software components for predictable integration and reusability in a new environment, in both hierarchical scheduling and RVN contexts.

Further, a multi-resource server (MRS) is proposed and implemented to enable predictable execution when composing multiple real-time components on a COTS multicore platform. MRS uses resource reservation for both CPU-bandwidth and memory-bus bandwidth to bound the interferences between tasks running on the same core, as well as, between tasks running on different cores. The later could, without MRS, interfere with each other due to contention on a shared memory-bus and memory. The results indicated that MRS can be used to "encapsulate" legacy systems and to give them enough resources to fulfill their purpose. In the dissertation, the compositional schedulability analysis for MRS is also provided and an experimental study is performed to bring insight on the correlation between the server budgets.

We believe that the proposed approaches enable a faster software integration and support legacy reuse and that this work transcend the boundaries of software engineering and real-time systems.

In real-time embedded systems the components and components integration must satisfy both functional correctness and extra-functional correctness, such as satisfying timing properties. Deploying multiple real-time components on a physical node poses timing problems in components’s integration. These timing problems during integration further effect predictability and reusability of real-time components. We propose a novel concept of runnable virtual node (RVN) whose interaction with the environment is bounded both by a functional and a temporal interface, and the validity of its internal temporal behaviour is preserved when integrated with other components or when reused in a new environment. Our realization of RVN exploits the latest techniques for hierarchical scheduling framework to achieve temporal isolation, and the principles from component-based software-engineering to achieve functional isolation. Proof-of-concept case studies executed on an AVR based 32- bit micro-controller demonstrates the preserving of real-time properties within components for predictable integration and reusability in a new environment without altering its temporal behaviour in both hierarchical scheduling and RVN contexts. We also take a step ahead towards expanding the performance preserving servers’ concept for multicore platform on which the scheduling of real-time tasks is inherently unpredictable due to the contention for shared physical memory and caches. It results in proposing and implementation of a novel type of server, called Multi-Resource Server (MRS) which controls the access to both CPU and memory bandwidth resources such that the execution of real-time tasks become predictable. The MRS provides temporal isolation both between tasks running on the same core, as well as, between tasks running on different cores. Further, we provide the schedulability analysis for MRS to provide predictable performance when composing multiple components on a shared multi-core platform.

We present the concept of runnable virtual node (RVN) as a means to achieve predictable integration and reuse of executable real-time components in embedded systems. A runnable virtual node is a coarse-grained software component that provides functional and temporal isolation with respect to its environment. Its interaction with the environment is bounded both by a functional and a temporal interface, and the validity of its internal temporal behaviour is preserved when integrated with other components or when reused in a new environment. Our realization of RVN exploits the latest techniques for hierarchical scheduling to achieve temporal isolation, and the principles from component-based software-engineering to achieve functional isolation. It uses a two-level deployment process, i.e. deploying functional entities to RVNs and then deploying RVNs to physical nodes, and thus also gives development benefits with respect to composability, system integration, testing, and validation. In addition, we have implemented a server-based inter-RVN communication strategy to not only support the predictable integration and reuse properties of RVNs by keeping the communication code in a separate server, but also increasing the maintainability and flexibility to change the communication code without affecting the timing properties of RVNs. We have applied our approach to a case study, implemented in the ProCom component technology executing on top of a FreeRTOS-based hierarchical scheduling framework and present the results as a proof-of-concept.

This paper presents a runtime support to consolidate legacy together with other real-time applications, running a single instance of a real-time operating system (RTOS), and sharing system resources. In this context, we resort to the hierarchical scheduling framework (HSF) to provide tem- poral partitions for dierent applications, supporting their independent development and real-time analysis, thus resulting on a predictable inte- gration. In particular, the paper focuses on a constructive element, the legacy server that allows executing code that is unaware of the temporal partition within which it is deployed. Furthermore, we discuss the chal- lenges that need to be addressed to execute a legacy application in an HSF without modications to the original code. We focus on the chal- lenge of enabling sharing system resources, both hardware and software, as typically found in most industrial software systems. We propose a novel solution based on wrappers for the required RTOS system calls. We implement our ideas in a concrete implementation on FreeRTOS OS, taking advantage of a prior HSF implementation. The validation is performed by a proof-of-concept case study that shows a successful integration of a legacy application that uses shared resources in a system that executes other applications.