Robustness in Interaction Systems

We treat the effect of absence/failure of ports or components on properties of component-based systems. We do so in the framework of interaction systems, a formalism for component-based systems that strictly separates the issues of local behavior and interaction, for which ideas to establish properties of systems where developed. We propose to adapt these ideas to analyze how the properties behave under absence or failure of certain components or merely some ports of components. We demonstrate our approach for the properties local and global deadlock-freedom as well as liveness and local progress

A Component-oriented Framework for Autonomous Agents

The design of a complex system warrants a compositional methodology, i.e., composing simple components to obtain a larger system that exhibits their collective behavior in a meaningful way. We propose an automaton-based paradigm for compositional design of such systems where an action is accompanied by one or more preferences. At run-time, these preferences provide a natural fallback mechanism for the component, while at design-time they can be used to reason about the behavior of the component in an uncertain physical world. Using structures that tell us how to compose preferences and actions, we can compose formal representations of individual components or agents to obtain a representation of the composed system. We extend Linear Temporal Logic with two unary connectives that reflect the compositional structure of the actions, and show how it can be used to diagnose undesired behavior by tracing the falsification of a specification back to one or more culpable components

A Hybrid Approach to Causality Analysis

In component-based safety-critical systems, when a system safety property is violated, it is necessary to analyze which components are the cause. Given a system execution trace that exhibits component faults leading to a property violation, our causality analysis formalizes a notion of counterfactual reasoning (\what would the system behavior be if a component had been correct? ) and algorithmically derives such alternative system behaviors, without re-executing the system itself. In this paper, we show that we can improve precision of the analysis if 1) we can emulate execution of components instead of relying on their contracts, and 2) take into consideration input/output dependencies between components to avoid blaming components for faults induced by other components. We demonstrate the utility of the extended analysis with a case study for a closed-loop patient-controlled analgesia system

SpinCause : A Tool for Causality Checking

In this paper we present the SpinCause tool for causality checking of Promela and PRISM models. We give an overview of the capabilities of SpinCause and briefly sketch how the causality checking algorithms are integrated into the state-space exploration algorithms used for model checking. In addition we compare the runtime and memory needed for causality checking with the different state-space exploration algorithms and two newly proposed iterative causality checking approaches

Etablierung, Charakterisierung und Differenzierung von primären humanen Myoblastenzellkulturen

Einleitung: Für die funktionelle und ästhetische Rekonstruktion von Skelettmuskeldefekten im Kopf-Hals-Bereich stellt das Tissue Engineering Konzept einen vielversprechenden Lösungsansatz dar. Das Regenerationspotential für das Tissue Engineering von Skelettmuskulatur basiert auf der Proliferations- und Differenzierungsfähigkeit von humanen Muskelvorläuferzellen (Stammzellen). Aus diesem Grund wurde eine primäre humane Myoblastenzellkultur etabliert und charakterisiert, welche aus humanen Muskelbiopsien gewonnen wurde.Methoden: Primäre humane Myoblastenzellkulturen wurden aus Muskelbiopsien gewonnen. Der Reinheitsgrad der Zellkulturen wurde durch Immunfärbungen gegen das Intermediärfilament Desmin verifiziert. Das Proliferationsverhalten wurde mittels AlamarBlue®-Assay bestimmt. Die Charakterisierung der Differenzierung erfolgte auf Proteinebene mit alpha-sarcomeric-actin-Immunfärbungen und einem Assay gegen das Enzym Kreatinkinase. Auf der Genexpressionsebene wurden die Zellen an verschieden Zeitpunkten mit einer quantitativen RT-PCR gegen die Markergene MyoD, Myogenin, Myf5 und MHC charakterisiert.Ergebnisse: Aus humanen Skelettmuskelbiopsien konnte erfolgreich eine Myoblastenzellkultur etabliert wurden. Diese proliferierten und differenzierten zu mehrkernigen Myofibrillen unter standardisierten in-vitro Zellkulturbedingungen. Das Proliferationsverhalten sowie die Differenzierung konnten sowohl auf enzymatischer, also auch auf Protein- und Genexpressionsebene nachgewiesen werden.Schlussfolgerung: Im Rahmen dieser Arbeit konnte als Grundvoraussetzung für das Skelettmuskel- Tissue Engineering aus Muskelbiopsien eine primäre humane Myoblastenzellkultur etabliert und charakterisiert werden

A General Trace-Based Framework of Logical Causality

In component-based safety-critical embedded systems it is crucial to determine the cause(s) of the violation of a safety property, be it to issue a precise alert or to determine liability of component providers. In this paper we present an approach to blame components based on a single execution trace violating a safety property P. The diagnosis relies on counterfactual reasoning (what would have been the outcome if component C had behaved correctly?) to distinguish component failures that actually contributed to the outcome from failures that had little or no impact on the violation of P