Abstract Assurance cases offer a structured way to present arguments and evidence for certification of systems where safety and security are critical. However, creating and evaluating these assurance cases can be complex and challenging, even for systems of moderate complexity. Therefore, there is a growing need to develop new automation methods for these tasks. While most existing assurance case tools focus on automating structural aspects, they lack the ability to fully assess the semantic coherence and correctness of the assurance arguments. In prior work, we introduced the Assurance 2.0 framework that prioritizes the reasoning process, evidence utilization, and explicit delineation of counter-claims (defeaters) and counter-evidence. In this paper, we present our approach to enhancing Assurance 2.0 with semantic rule-based analysis capabilities using common-sense reasoning and answer set programming solvers, specifically s(CASP). By employing these analysis techniques, we examine the unique semantic aspects of assurance cases, such as logical consistency, adequacy, indefeasibility, etc. The application of these analyses provides both system developers and evaluators with increased confidence about the assurance case.

In the safety-critical domain, such as avionics, there is a strong demand for increased guaranteed performance and lower development costs. This demand is satisfied by utilizing commercial off-the-shelf (COTS) Multiprocessor System-on-Chips (MPSoC). MPSoCs contain multi-core processors that pose a significant challenge for deployment in safety-critical systems, since the Worst-Case Execution Time (WCET) of a process may be influenced by other processes due to cross-core interference.In this paper, we introduce a novel non-intrusive IP Core for Cache and Memory Thrashing (referred to as IP-CMT) that helps us estimate the cross-core interference. The IP-CMT core does not require any software changes to be made to the system under test, resulting in lower development costs. Furthermore, our evaluation with a real-world aerospace-grade Flight Management System indicates that the proposed IP-CMT core is capable of introducing the same degree of cross-core interference as present-day SW methods while not being overly conservative and having minimal overhead. Thus, system performance is spared.

TTEthernet is a novel communication infrastructures that allows using a single physical communication infrastructure for distributed applications with mixed-criticality requirements, e.g. the command and control systems and audio/video systems. This is achieved via a fault-tolerant self-stabilizing synchronization strategy, which establishes temporal partitioning and, hence, ensures isolation of the critical dataflows from the non-critical dataflows. The focus in this paper is on the dataflow in TTEthernet. For this we take the synchronization as a given and discuss from a TTEthernet user perspective which communication options TTEthernet provides and how they are aligned and realized. While this paper uses TTEthernet as reference communication infrastructure, the methods and strategies presented are valid for any message-based network.

With the growing popularity of the Internet, there is increasing interest in using it for audio and video transmission. Perceptual studies of audio and video viewing have shown that viewers find bursty losses, mostly caused by congestion, to be the most annoying disturbance, and hence these are critical issues to be addressed for continuous media streaming applications. Classical error handling techniques have mostly been geared toward ensuring that the transmission is correct, with no attention to timeliness. For isochronous traffic like audio and video, timeliness is a key criterion, and given the high degree of content redundancy, some loss of content is quite acceptable. We introduce the concept of error spreading, which is a transformation technique that permutes the input sequence of packets (from a continuous stream of data) before transmission. The packets are unscrambled at the receiving end. The transformation is designed to ensure that bursty losses in the transformed domain get spread all over the sequence in the original domain, thus improving the perceptual quality of the stream. Our error spreading idea deals with both cases where the stream has or does not have inter-frame dependencies. We next describe a continuous media transmission protocol and experimentally validate its performance based on this idea. We also show that our protocol can be used complementary to other error handling protocols.

For transmission of continuous media (CM) streams such as audio and video over the Internet, a critical issue is that periodic network overloads cause bursty packet losses. Studies on human perception of audio and video streams have shown that bursty losses have the most annoying affects. Hence, addressing this issue is critical for multimedia applications such as Internet telephony, videoconferencing, distance learning, etc. Classical error handling schemes like retransmission and forward error recovery have the undesirable effects of (a) introducing timing variations, which is unacceptable for isochronous traffic, and (b) using up valuable bandwidth, potentially exacerbating the problem. This paper introduces a new concept called error spreading, which is a transformation technique that takes an input sequence of packets (from an audio or video stream) and permutes them before transmission. The packets are then un-permuted at the receiver before delivery to the application. The purpose is to spread out bursty network errors, in order to achieve better perceptual quality of the transmitted stream. Analysis has been done to determine the provable lower bound on bursty errors tolerable by this class of protocols. An algorithm to generate the optimal permutation for a given network loss rate is presented. While our previous work had focused on streams with no inter-frame dependencies, e.g. MJPEG encoded video, in this paper the technique is generalized to streams with inter-frame dependencies, e.g. MPEG encoded video.