AIOCJ: A Choreographic Framework for Safe Adaptive Distributed Applications

We present AIOCJ, a framework for programming distributed adaptive applications. Applications are programmed using AIOC, a choreographic language suited for expressing patterns of interaction from a global point of view. AIOC allows the programmer to specify which parts of the application can be adapted. Adaptation takes place at runtime by means of rules, which can change during the execution to tackle possibly unforeseen adaptation needs. AIOCJ relies on a solid theory that ensures applications to be deadlock-free by construction also after adaptation. We describe the architecture of AIOCJ, the design of the AIOC language, and an empirical validation of the framework.Comment: Technical Repor

Heterogeneous Timed Machines

International audienceWe present an algebra of discrete timed input/output au- tomata that execute in the context of different clock granularities -- timed machines -- as models of systems that can be dynamically inter- connected at run time in a heterogeneous context. We show how timed machines can be refined to a lower granularity of time and how timed machines with different clock granularities can be composed. We propose techniques for checking whether timed machines are consistent or feasi- ble. Finally, we investigate how consistency and feasibility of composition can be proved at run-time without computing products of automata

An Abstract Framework for Deadlock Prevention in BIP

Part 6: Session 5: Model CheckingInternational audienceWe present a sound but incomplete criterion for checking deadlock freedom of finite state systems expressed in BIP: a component-based framework for the construction of complex distributed systems. Since deciding deadlock-freedom for finite-state concurrent systems is PSPACE-complete, our criterion gives up completeness in return for tractability of evaluation. Our criterion can be evaluated by model-checking subsystems of the overall large system. The size of these subsystems depends only on the local topology of direct interaction between components, and not on the number of components in the overall system. We present two experiments, in which our method compares favorably with existing approaches. For example, in verifying deadlock freedom of dining philosphers, our method shows linear increase in computation time with the number of philosophers, whereas other methods (even those that use abstraction) show super-linear increase, due to state-explosion

Substrate specificity of a peptidyl-aminoacyl-l/d-isomerase from frog skin

In the skin of fire-bellied toads (Bombina species), an aminoacyl-l/d-isomerase activity is present which catalyses the post-translational isomerization of the l- to the d-form of the second residue of its substrate peptides. Previously, this new type of enzyme was studied in some detail and genes potentially coding for similar polypeptides were found to exist in several vertebrate species including man. Here, we present our studies to the substrate specificity of this isomerase using fluorescence-labeled variants of the natural substrate bombinin H with different amino acids at positions 1, 2 or 3. Surprisingly, this enzyme has a rather low selectivity for residues at position 2 where the change of chirality at the alpha-carbon takes place. In contrast, a hydrophobic amino acid at position 1 and a small one at position 3 of the substrate are essential. Interestingly, some peptides containing a Phe at position 3 also were substrates. Furthermore, we investigated the role of the amino-terminus for substrate recognition. In view of the rather broad specificity of the frog isomerase, we made a databank search for potential substrates of such an enzyme. Indeed, numerous peptides of amphibia and mammals were found which fulfill the requirements determined in this study. Expression of isomerases with similar characteristics in other species can therefore be expected to catalyze the formation of peptides containing d-amino acids

Contracts for BIP: Hierarchical Interaction Models for Compositional Verification

This paper presents an extension of the BIP component framework to hierarchical components by considering also port sets of atomic components to be structured (ports may be in conflict or ordered, where a larger port represents an interaction set with larger interactions). A composed component consisting of a set of components connected through BIP connectors and a set of ports representing a subset of the internal connectors and ports, has two semantics: one in terms if interactions as defined by the BIP semantics, and one in terms of the actions represented by external ports where the structure of the port set of the component is derived from the internal structure of the component. A second extension consists in the addition of implicit interactions which is done through an explicit distinction of conflicting and concurrent ports: interactions involving only non conflicting ports can be executed concurrently without the existence of an explicit connector. Finally, we define contract-based reasoning for component hierarchies

C.: A Polynomialtime Checkable Sufficient Condition for Deadlock-Freedom of Component-based Systems

Abstract. Interaction systems are a formal model for component-based systems. Combining components via connectors to form more complex systems may give rise to deadlock situations. Deciding the existence of deadlocks is NP-hard as it involves global state analysis. We present here a parametrized polynomial-time algorithm that is able to confirm deadlock-freedom for a certain class of interaction systems. The discussion includes characteristic examples and displays the role of the parameter of the algorithm.

Differenzielle Expression von Matrix-Komponenten humaner Chondrozyten während in vitro Dedifferenzierung

Einleitung: Die Generierung einer Knorpelmatrix spielt für die Herstellung von Transplantaten in der plastisch-rekonstruktiven Chirurgie eine wesentliche Rolle. Während einer Chondrozytenkultur spielt die Dedifferenzierung eine entscheidende Rolle für die Zellvermehrung. Die dedifferenzierenden Zellen bilden jedoch Matrix von nur geringer Qualität. Die molekularen Grundlagen der Zusammenhänge sind bisher nur unvollständig bekannt. Das Ziel dieser Arbeit war daher die Untersuchung der Expression von Matrix-Komponenten humaner Chondrozyten während der Dedifferenzierung.Methoden: Humane Chondrozyten wurden aus dem Nasenseptum (n=32) gewonnen und in primärer Zellkultur gezüchtet. Die Untersuchung erfolgte nach 1, 6 und 21 Tagen. Die Zelldifferenzierung wurde mittels Lichtmikroskopie, die Expressionsmuster verschiedener Proteine (MMP, TIMP) durch Immunohistochemie und die Expressionen bestimmter Gene unter Nutzung der Microarray-Technik analysiert.Ergebnisse: Die Regulation der Expression von MMP-2, -3 und -13 stieg von Tag 1 bis Tag 21, wohingegen eine Reduktion von MMP-12 und MMP-20 beobachtet wurde. Es erfolgte keine Expression weiterer MMPs. TIMP-1 wurde während der Expansion ebenfalls aktiviert, unterdessen sank die Expression von TIMP-3.Schlussfolgerung: Die differenzielle Expression verschiedener Matrix-Komponenten scheint die Zusammensetzung einer artifiziell hergestellten Knorpel-Zellmatrix zu beeinflussen. Eine grundlegende Kenntnisserweiterung in diesem Bereich könnte zu einer wesentlichen Verbesserung bei der Identifikation und daraus resultierenden Interventionen zur Vermeidung eines Stabilitätsverlustes von bioartrifiziell hergestelltem Knorpelgewebe führen