CSP as a Coordination Language. A CSP-based Approach to the Coordination of Concurrent Systems

Die Beherrschbarkeit komplexer nebenläufiger Systeme hängt in hohem Maße davon ab, mit welchen Methoden das System modelliert bzw. spezifiziert wird. Formale auf Nebenläufigkeit spezialisierte Methoden erlauben es, solche Systeme elegant auf einem hohen Abstraktionsniveau zu modellieren und zu analysieren. Ein Vertreter derartiger Methoden ist die in dieser Arbeit verwendete Prozess Algebra CSP. CSP ist ein weitverbreiteter, wohluntersuchter Formalismus, der es erlaubt, ein nebenläufiges System mathematisch präzise zu beschreiben und wichtige Eigenschaften, beispielsweise Verklemmungsfreiheit, zu verifizieren. Dennoch ist die Ableitung einer Systemimplementierung aus einem gegebenen CSP Modell immer noch ein aktueller Forschungsgegenstand. So ist zum Beispiel unklar, wie interne Aktionen eines Systems in einer Implementierung integriert werden können, da diese in CSP ununterscheidbar sind. Als Lösung wird in dieser Arbeit vorgeschlagen, CSP mit einer sequentiellen Zielsprache zu integrieren, so dass die Aktionen eines Systems in der sequentiellen Zielsprache implementiert werden und die Aktionen entsprechend eines CSP Prozesses koordiniert werden. Koordinationssprachen zielen ebenfalls darauf ab, Nebenläufigkeit von sequentiellen Aspekten eines Systems zu trennen, sie sind aber weniger auf automatisierte formale Verifikation ausgerichtet. In der Arbeit wird die Verwendung der Prozess Algebra CSP als formale Koordinationssprache für beliebige sequentielle Zielsprachen vorgeschlagen. Hierfür wird das formale Fundament einer Koordinationsumgebung entwickelt, die einen CSP Prozess zur Laufzeit simuliert und die Aktionen des Systems entsprechend ausführt. Besonderer Wert liegt auf der Koordination interner Aktionen und auf der Erkennung von Nebenläufigkeit zwischen extern synchronisierbaren und internen Aktionen. Durch Beweisverpflichtungen wird der Zusammenhang zwischen dem Koordinationsprozess und den Implementierungen der Aktionen hergestellt. Die Koordinationsumgebung wird konkret für die Zielsprache Java implementiert. Desweiteren wird eine Fallstudie vorgestellt, die sich mit der Entwicklung eines Workflow Servers beschäftigt, dessen interne Nebenläufigkeit einerseits selbst mittels CSP koordiniert wird und der andererseits CSP-basierte Workflows ausführen kann, die ebenfalls durch eine CSP Koordinationsumgebung gesteuert werden. Die Arbeit enthält wissenschaftliche Beiträge zur Theorie und der praktischen Verwendbarkeit von CSP, bezüglich der Konstruktion korrekter nebenläufiger Systeme, sowie zum Bereich der Modellierung und Verwaltung von Workflows.Complex concurrent systems are in general hard to understand, and equally hard to specify and to verify. The process algebra Communicating Sequential Processes (CSP) offers a way of taming the complexity of concurrent systems by focusing on the interaction behavior of systems and abstracting from synchronization mechanisms and other implementation details. CSP provides a mature intermediate level formalism that allows us to specify and model such systems in a mathematically precise way and to verify important properties, e. g., deadlock-freedom. However, the derivation of a system’s implementation from its CSP-based model is still a problem and sub ject to ongoing research. It is, for example, not obvious how to integrate CSP with internal actions of a system, because CSP abstracts from internal actions to a great extent. To overcome this problem, we propose to integrate CSP with a sequential host language such that the concurrency aspects of systems are captured on the CSP level and its actions are implemented in the sequential host language. This idea of separating concurrent and sequential aspects of a system is also known from coordination languages, but those are in general less amenable to automated verification. In this thesis, we present the use of CSP as a formal coordination language for arbitrary sequential host languages, allowing us to use CSP for the design, implementation, and verification of concurrent systems. To this end, we develop the model of a coordination environment that simulates a CSP process at runtime and performs the system’s actions accordingly. The coordination environment controls the system’s interaction with its environment as well as its internal actions. We present proof obligations to ensure that the properties proved on the CSP level also hold on the implementation level of the system. We also present an implementation of the coordination environment for the target language Java and a case study of constructing a workflow server as a coordinated concurrent Java program. This thesis contributes to the theory and practice of CSP, to the engineering of correct concurrent systems, and to the modeling and management of workflows. The main contribution of this thesis is a target language independent CSP-based framework for the construction of provably correct concurrent systems

Clinical Application of the Hanover Classification for Iatrogenic Bile Duct Lesions

Background. There is only limited evidence available to justify generalized clinical classification and treatment recommendations for iatrogenic bile duct lesions. Methods. Data of 93 patients with iatrogenic bile duct lesions was evaluated retrospectively to analyse the variety of encountered lesions with the Hanover classification and its impact on surgical treatment and outcomes. Results. Bile duct lesions combined with vascular lesions were observed in 20 patients (21.5%). 18 of these patients were treated with additional partial hepatectomy while the majority were treated by hepaticojejunostomy alone (n = 54). Concomitant injury to the right hepatic artery resulted in additional right anatomical hemihepatectomy in 10 of 18 cases. 8 of 12 cases with type A lesions were treated with drainage alone or direct suture of the bile leak while 2 patients with a C2 lesion required a Whipple's procedure. Observed congruence between originally proposed lesion-type-specific treatment and actually performed treatment was 66–100% dependent on the category of lesion type. Hospital mortality was 3.2% (n = 3). Conclusions. The Hannover classification may be helpful to standardize the systematic description of iatrogenic bile duct lesions in order to establish evidence-based and lesion-type-specific treatment recommendations

Adult Kasabach-Merritt Syndrome due to Hepatic Giant Hemangioma

Cavernous hemangiomas are the most common benign tumors of the liver. They can reach enormous sizes and cause various complications. Kasabach-Merritt syndrome is a rare but serious complication characterized by consumptive coagulopathy caused by the hemangioma; mortality rate ranges between 10 and 37%. More than 80% of cases occur within the first year of life. Goals of the treatment are to control the coagulopathyand thrombocytopenia as well as to eradicate the hemangioma. Different nonsurgical treatment regimens are performed, includingsystemic corticosteroids, irradiation and various chemicals. Surgery should be limited to symptomatic or complicated cases. Although difficult, resection of the tumor is usually curative. Here we present a 44-year-old woman with giant hepatic hemangioma causing Kasabach-Merritt syndrome managed by enucleation

Permanent biventricular ICD-implantation in a heart failure second re-do-CABG patient: a case report

Biventricular pacing has been suggested in end-stage heart failure. We present a 59-year-old patient undergoing second re-do CABG (coronary artery bypass graft) and carotid artery endarterectomy. Ejection fraction was 15%, QRS-width 175 ms. Following the carotid and CABG procedure, an implanted single-chamber ICD (implantable cardioverter defibrillator) was upgraded to permanent biventricular DDD pacing by implantation of one epicardial left ventricular and one epicardial atrial electrode. At follow-up two months postoperatively ejection fraction had significantly improved to 45%, the patient underwent stress test with adequate load and reported a good quality of life

Reconstruction and subsurface lattice distortions in the (2 × 1)O-Ni(110) structure: A LEED analysis

LEED analysis of the reconstructed (2 × 1)O-Ni(110) system clearly favors the “missing row” structure over the “saw-tooth” and “buckled row” models. By using a novel computational procedure 8 structural parameters could be refined simultaneously, leading to excellent R-factors (RZJ = 0.09, RP = 0.18). The adsorbed O atoms are located 0.2 Å above the long bridge sites in [001] direction, presumably with a slight displacement ( 0.1 Å) in [1 0] direction to an asymmetric adsorption site. The nearest-neighbor Ni---O bond lengths (1.77 Å) are rather short. The separation between the topmost two Ni layers is expanded to 1.30 Å (bulk value 1.25 Å), while that between the second and third layer is slightly contracted to 1.23 Å. The third layer is, in addition, slightly buckled (±0.05 Å). The results are discussed on the basis of our present general knowledge about the structure of adsorbate covered metallic surfaces

Etiology and Outcome of Adult and Pediatric Acute Liver Failure in Europe

Acute liver failure (ALF) is rare but life-threatening. Common causes include intoxications, infections, and metabolic disorders. Indeterminate etiology is still frequent. No systematic data on incidence, causes, and outcome of ALF across Europe are available. Via an online survey we reached out to European Reference Network Centers on rare liver diseases. Numbers and etiology of ALF cases during 2020 were retrieved and diagnostic and treatment availabilities assessed. In total, 455 cases (306 adult, 149 pediatric) were reported from 36 centers from 20 countries. Intoxication was the most common cause in adult and pediatric care. The number of cases with indeterminate etiology is low. Diagnostic tools and specific treatment options are broadly available within this network. This is the first approach to report on etiology and outcome of ALF in the pediatric and adult population in Europe. High diagnostic yield and standard of care reflects the expert status of involved centers.</p

Integration of time-series meta-omics data reveals how microbial ecosystems respond to disturbance.

The development of reliable, mixed-culture biotechnological processes hinges on understanding how microbial ecosystems respond to disturbances. Here we reveal extensive phenotypic plasticity and niche complementarity in oleaginous microbial populations from a biological wastewater treatment plant. We perform meta-omics analyses (metagenomics, metatranscriptomics, metaproteomics and metabolomics) on in situ samples over 14 months at weekly intervals. Based on 1,364 de novo metagenome-assembled genomes, we uncover four distinct fundamental niche types. Throughout the time-series, we observe a major, transient shift in community structure, coinciding with substrate availability changes. Functional omics data reveals extensive variation in gene expression and substrate usage amongst community members. Ex situ bioreactor experiments confirm that responses occur within five hours of a pulse disturbance, demonstrating rapid adaptation by specific populations. Our results show that community resistance and resilience are a function of phenotypic plasticity and niche complementarity, and set the foundation for future ecological engineering efforts