Dimension-Based Subscription Pruning for Publish/Subscribe Systems

Subscription pruning has been proven as valuable routing optimization for Boolean subscriptions in publish/ subscribe systems. It aims at optimizing subscriptions independently of each other and is thus applicable for all kinds of subscriptions regardless of their individual and collective structures. The original subscription pruning approach tries to optimize the event routing process based on the expected increase in network load. However, a closer look at pruning-based routing reveals its further applicability to optimizations in respect to other dimensions. In this paper, we introduce and investigate subscription pruning based on three dimensions of optimization: network load, memory usage, and system throughput. We present the algorithms to perform prunings based on these dimensions and discuss the results of a series of practical experiments. Our analysis reveals the advantages and disadvantages of the different dimensions of optimization and allows conclusions about the suitability of dimension-based pruning for different application requirements

Event distributions in online book auctions.

Current quantitative evaluations in various research areas for publish/ subscribe systems use artificially created event messages to model the system workload. The assumptions made to create these workloads are rather strong and hardly ever described in detail. This does not allow for a repetition of experiments or comparative evaluations of different approaches by different researches. In this paper, we present an evaluation of the distributions of the values of attributes typically used in online auction scenarios. In particular, we focus on auctions of fiction books. We further show our approach of creating event messages by the help of the gained information. Publishing this information on how to create a typical workload for online auctions should allow for the repetition of experiments and the comparison of different evaluations

Arbitrary boolean advertisements: the final step in supporting the boolean publish/subscribe model

Publish/subscribe systems allow for an efficient filtering of incoming information. This filtering is based on the specifications of subscriber interests, which are registered with the system as subscriptions. Publishers conversely specify advertisements, describing the messages they will send later on. What is missing so far is the support of arbitrary Boolean advertisements in publish/subscribe systems. Introducing the opportunity to specify these richer Boolean advertisements increases the accuracy of publishers to state their future messages compared to currently supported conjunctive advertisements. Thus, the amount of subscriptions forwarded in the network is reduced. Additionally, the system can more time efficiently decide whether a subscription needs to be forwarded and more space efficiently store and index advertisements. In this paper, we introduce a publish/subscribe system that supports arbitrary Boolean advertisements and, symmetrically, arbitrary Boolean subscriptions. We show the advantages of supporting arbitrary Boolean advertisements and present an algorithm to calculate the practically required overlapping relationship among subscriptions and advertisements. Additionally, we develop the first optimization approach for arbitrary Boolean advertisements, advertisement pruning. Advertisement pruning is tailored to optimize advertisements, which is a strong contrast to current optimizations for conjunctive advertisements. These recent proposals mainly apply subscription-based optimization ideas, which is leading to the same disadvantages. In the second part of this paper, our evaluation of practical experiments, we analyze the efficiency properties of our approach to determine the overlapping relationship. We also compare conjunctive solutions for the overlapping problem to our calculation algorithm to show its benefits. Finally, we present a detailed evaluation of the optimization potential of advertisement pruning. This includes the analysis of the effects of additionally optimizing subscriptions on the advertisement pruning optimization

On the Benefits of Non-Canonical Filtering in Publish/Subscribe Systems

Current matching approaches in pub/sub systems only allow conjunctive subscriptions. Arbitrary subscriptions have to be transformed into canonical expressions, e.g., DNFs, and need to be treated as several conjunctive subscriptions. This technique is known from database systems and allows us to apply more efficient filtering algorithms. Since pub/sub systems are the contrary to traditional database systems, it is questionable if filtering several canonical subscriptions is the most efficient and scalable way of dealing with arbitrary subscriptions. In this paper we show that our filtering approach supporting arbitrary Boolean subscriptions is more scalable and efficient than current matching algorithms requiring transformations of subscriptions into DNFs

Investigating the memory requirements for publish/subscribe filtering algorithms

Various filtering algorithms for publish/subscribe systems have been proposed. One distinguishing characteristic is their internal representation of Boolean subscriptions: They either require conversions to disjunctive normal forms (canonical approaches) or are directly exploited in event filtering (non-canonical approaches). In this paper, we present a detailed analysis and comparison of the memory requirements of canonical and non-canonical filtering algorithms. This includes a theoretical analysis of space usages as well as a verification of our theoretical results by an evaluation of a practical implementation. This practical analysis also considers time (filter) efficiency, which is the other important quality measure of filtering algorithms. By correlating the results of space and time efficiency, we conclude when to use non-canonical and canonical approaches

General Boolean Expressions in Publish-Subscribe Systems

The increasing amount of electronically available information in society today is undeniable. Examples include the numbers of general web pages, scientific publications, and items in online auctions. From a user's perspective, this trend will lead to information overflow. Moreover, information publishers are compromised by this situation, as users have greater difficulty in identifying useful information. Publish-subscribe systems can be applied to cope with the reality of information overflow. In these systems, users specify their information interests as subscriptions and, subsequently, only matching information (event messages) is delivered; uninteresting information is filtered out before reaching users. In this dissertation, we consider content-based publish-subscribe systems, a sophisticated example of these systems. They perform the information-filtering task based on the content of provided information. In order to deal with high numbers of subscriptions and frequencies of event messages, publish-subscribe systems are realized as distributed systems. Advertisements---publisher specifications of potential future event messages---are optionally applied in these systems to reduce the internal distribution of subscriptions. Existing work on content-based publish-subscribe concepts mainly focuses on subscriptions and advertisements as pure conjunctive expressions. Therefore, subscriptions or advertisements using operators other than conjunction need to be canonically converted to disjunctive normal form by these systems. Each conjunctive component is then treated as individual subscription or advertisement. Unfortunately, the size of converted expressions is exponential in the worst case. In this dissertation, we show that the direct support of general Boolean subscriptions and advertisements improves the time and space efficiency of general-purpose content-based publish-subscribe systems. For this purpose, we develop suitable approaches for the filtering and routing of general Boolean expressions in these systems. Our approaches represent solutions to exactly those components of content-based publish-subscribe systems that currently restrict subscriptions and advertisements to conjunctive expressions. On the subscription side, we present an effective generic filtering algorithm, and a novel approach to optimize event routing tables, which we call subscription pruning. To support advertisements, we show how to calculate the overlap between subscriptions and advertisements, and introduce the first designated subscription routing optimization, which we refer to as advertisement pruning. We integrate these approaches into our prototype BoP (BOolean Publish-subscribe) which allows for the full support of general Boolean expressions in its filtering and routing components. In the evaluation part of this dissertation, we empirically analyze our prototypical implementation BoP and compare its algorithms to existing conjunctive solutions. We firstly show that our general-purpose Boolean filtering algorithm is more space- and time-efficient than a general-purpose conjunctive filtering algorithm. Secondly, we illustrate the effectiveness of the subscription pruning routing optimization and compare it to the existing covering optimization approach. Finally, we demonstrate the optimization effect of advertisement pruning while maintaining the existing overlapping relationships in the system

Ermittlung der Schwermetallabgabe (Run-off) metallischer Werkstoffe infolge atmosphärischer Korrosion, insbesondere bei Blei, Kupfer und Zink.

The toxic effect of heavy metals for man and his environment is well known for many years. But investigations about concentrations of heavy metals in run-off waters from roofs, pipes and other roofing materials are still missing until today, although they can reach critical concentrations. The reaction mechanisms which are responsible for the release of those metals due to precipitation should be investigated by means of on lead-, copper-, zinc- and zinced steel sheets. For these purposes expositions at selected test sites (Bottrop and Munich) have been conducted for a period of two years in free nature and in addition under laboratory conditions. The main difference to former expositions of materials is in fact that his investigation is not focused on the blanket mass loss of metals but rather on the release of heavy metal ions from lead, copper and zinc from the mentioned metals and alloys. Following the project´s concept samples of the run-off waters from both test-sites were taken in periodic intervals. The concentrations of heavy metals were measured in order to determine the run-off rates. Together with the analysis of the water samples the most important atmospheric parameters at both test sites were recorded during the exposition period to reveal specific correlations between climatic data and heavy metal concentrations. These correlations should provide a basis for the calculation of dose-response-functions. The necessary climatic data were made available from the local environ-mental authorities. The calculated dose-response-functions were based on measured values from two test-sites, which are very different to each other, considering atmospheric conditions and geographical situation, Bottrop (Ruhr-Area) and Munich (Bavaria). These dose-response-relations can be used for the development of maps of stock at risk to predict expected run-off rates under defined conditions. One should keep in mind, these calculated dose-response-functions provide run-off rates, which interpolate over a great range of different atmospheric and geographical conditions. Regarding the dose-response-functions preference was put on reaching a preferably high quality level (in this case the global maximum correlation-coefficient R2 ) by a small number of easily accessable parameters. The determined gravimetric parameters can be compared to related research-programmes, in which the Bavarian State Department of Historical Monuments and the Federal Environmental Agency (UBA, Berlin) have participated for many years. Parallel to the expositions laboratory experiments have been conducted. These laboratory experiments provide insight into run-off behaviour under defined conditions. Due to the fact that the exposition and the laboratory experiments were very different to each other the results of the laboratory experiments were not considered for the calculation of the dose-response-functions. The emphasis of the first laboratory experiment was to search into the relation between inclination and relative humidity. This experiment provided a new under-standing of the so-called “first flush”-effect. The results of this test series are that the “first flush”-effect preferentially appears at a relative humidity of 60%, independent of inclination. Higher humidities and different inclinations appear to have no influence on the release of heavy-metals. Aim of the second laboratory experiment was to clarify the influence of distance on the saturation of a waterdrop with metal ions. As a result of these experiments it was found that there was a measured relation between distance and concentration of heavy metals, insofar the water was not saturated before reaching the end of the running distance. With an irrigation time of 10 minutes at nearly equal feeding rates, saturation with heavy metals was reached in most cases depending on the metal. The third experiment was concentrating on the saturation rate of a not moving water drop with heavy metal ions. Regarding the concentrations over an experiment time of seven days it is to determine that the water drops have saturated themselves in shortest time (6-24 hours). Conditional on the results of the third laboratory experiments a fourth test series was conducted. Within the scope of this test series, saturation rates and saturation concentrations of different metals could be determined by contact times until 6 hours. Summarising it is to remark, that the results which have been gathered in this work are contributing to a better understanding of chemical and physical processes which affect a metal surface due to corrosion.Die toxische Wirkung von Schwermetallen für den Menschen und seine Umwelt ist seit langem bekannt. Es fehlen aber bis heute Untersuchungen über die Konzentrationen der Schwermetalle in den Ablaufwässern von Dächern, Gesims-verwahrungen und anderen Metallbauteilen, welche in Anbetracht der engen Grenzwerte kritische Konzentrationen erreichen können. Mit Hilfe der Untersuchungen an Blei-, Kupfer-, Zink- und verzinktem Eisenblech sollten die Reaktionsmechanismen untersucht werden, nach denen die betreffenden Schwermetalle bei Regenereignissen freigesetzt werden und in die Umwelt gelangen. Zu diesem Zweck wurden Freibewitterungen an ausgewählten Expositionsstandorten (Bottrop und München) in der freien Umwelt über einen Zeitraum von zwei Jahren und ergänzend im Labor durchgeführt. Der wesentliche Unterschied zu den meisten bisherigen Materialexpositionen liegt in der Tatsache, dass nicht der pauschale Materialverlust, sondern die Freisetzung von Schwermetallionen wie Blei, Kupfer, Zink und verzinktem Stahl aus den betreffenden Metallen und Legierungen bestimmt wurde. Der Konzeption des Vorhabens folgend, wurden an beiden Standorten in regel-mäßigen Abständen Proben der Ablaufwässer genommen und auf deren Gehalt an Schwermetallen untersucht, um Metallabtragsraten zu ermitteln. Begleitend wurden an beiden Standorten die wichtigsten atmosphärischen Para-meter während der Freibewitterung aufgezeichnet, um spezifische Korrelationen als Grundlage für die Abschätzung von Dosis-Wirkungs-Beziehungen erkennen zu können. Die benötigten Daten wurden von den zuständigen Umweltbehörden zur Verfügung gestellt. Die in dieser Arbeit ermittelten Dosis-Wirkungs-Beziehungen wurden auf Grundlage der Messdaten zweier Standorte berechnet, deren Charakteristika (atmosphärische Parameter) hinsichtlich ihrer geographischen Lage (Bottrop (Ruhrgebiet) und München (Oberbayern)) sehr unterschiedlich sind. Die berechneten Dosis-Wirkungs-Beziehungen können als Basis für die Entwicklung von Schadens-Risiko-Karten herangezogen werden, um zu erwartende Schwer-metallabträge unter definierten Umweltbedingungen abzuschätzen. Aus oben genannten Gründen wird zu Bedenken gegeben, dass die errechneten Dosis-Wirkungs-Beziehungen sowohl in geographischer als auch in atmosphärischer Hinsicht Abtragsraten liefern, die über einen relativ großen Bereich interpolieren. Aus praktischen Gründen wurde bei der Entwicklung der Dosis-Wirkungs-Bezieh-ungen Wert darauf gelegt, einen möglichst hohen qualitativen Standard (hier der globale maximale Korrelationskoeffizient R2) mit einer geringen Anzahl an leicht erfassbaren Parametern zu erreichen. Die ermittelten gravimetrischen Parameter können zu Vergleichen mit themen-verwandten Forschungsvorhaben, in welchen das Bayerische Landesamt für Denk-malpflege und das Umweltbundesamt seit Jahren beteiligt sind, herangezogen werden. Parallel zu den Freibewitterungen wurden Laborversuche durchgeführt, die neue Erkenntnisse über das Abflussverhalten unter definierten Bedingungen ergaben. Da die Konzeption der Laborversuche und der kontinuierlichen Freibewitterung jedoch sehr unterschiedlich ausfielen, fanden die Ergebnisse der Laborversuche in den Dosis-Wirkungs-Beziehungen keine Anwendung. Die erste Laborversuchsanordnung, deren Schwerpunkt im Zusammenhang zwischen Neigungswinkel und relativer Luftfeuchte lag, brachte neue Erkenntnisse über den sogenannten „First-Flush“-Effekt. Ergebnis dieser Versuchsreihe war, dass dieser „First-Flush“-Effekt bevorzugt bei einer relativen Luftfeuchte um 60% auftritt und dies unabhängig vom Neigungs-winkel. Höhere Luftfeuchten und Neigungswinkel übten in dieser Versuchsreihe keinen Einfluss auf die Freisetzung von Schwermetallen aus. Gegenstand der zweiten Laborversuchsanordnung war der Einfluss der Lauflänge eines Wassertropfens auf dessen Sättigung mit Metallionen. Als Resultat dieser Versuche gilt festzuhalten, dass bei gleichen Probenvolumen (hier 100 ml) ein Zusammenhang zwischen Lauflänge und Schwermetallkonzen-tration ermittelt werden konnte, sofern sich die Probenmenge nicht schon vorher an Metallionen gesättigt hatte. Bei 10 Minuten Bewässerung mit annähernd gleicher Förderrate wurden meist (abhängig vom Metall) die Sättigungsgrade erreicht, so dass sich die Konzentra-tionen auf einen konstanten Wert einpendelten. Die dritte Versuchsreihe konzentrierte sich auf die Geschwindigkeit, mit der sich ein stehender Wassertropfen mit Metallionen anreichert. Betrachtet man die Konzentrationen über sieben Tage Versuchsdauer, so lässt sich feststellen, dass sich die Wassertropfen schon nach kürzester Zeit (6 - 24 Stunden) gesättigt haben und bedingt durch Inhomogenitäten auf der Metalloberfläche um diesen Sättigungswert streuen. Bedingt durch die Ergebnisse der dritten Laborversuchsanordnung, wurde noch eine vierte Versuchsreihe durchgeführt. Im Rahmen dieser Reihe konnten bei Kontakt-zeiten von 1 Minute bis zu 6 Stunden Anreicherungsgeschwindigkeiten sowie Sätti-gungsbereiche der einzelnen Metalle ermittelt werden. Zusammenfassend gilt zu bemerken, dass die Ergebnisse, die in dieser Arbeit gesammelt wurden, einen Beitrag zu einem besseren Verständnis der chemischen und physikalischen Prozesse, die im Rahmen der Korrosion auf ein Metall einwirken, leisten

Hardware Accelerating the Optimization of Transaction Schedules via Quantum Annealing by Avoiding Blocking

The isolation property of database theory guarantees to avoid problems of not synchronized parallel execution of several transactions. In this paper we propose an algorithm for an optimal transaction schedule for the different cores of a multi-core CPU with minimal execution time ensuring the isolation property. Optimizing the transaction schedule is a combinatorial problem, which is ideal to be solved by quantum annealers as special form of quantum computers. In our contribution we show how to transform an instance of the transaction schedule problem into a formula that is accepted by quantum annealers including a proof of validity and optimality of the obtained result. Furthermore, we analyze the number of required qubits and the preprocessing time, and introduce an approach for caching formulas as result of preprocessing for the purpose of reducing the preprocessing time. In an experimental evaluation, the runtime on a quantum annealer outperforms the runtime of traditional algorithms to solve combinatorial problems like simulated annealing already for small problem sizes

A detailed investigation of memory requirements for publish/subscribe filtering algorithms

Various filtering algorithms for publish/subscribe systems have been proposed. One distinguishing characteristic is their internal representation of Boolean subscriptions: They either require conversions into DNFs (canonical approaches) or are directly exploited in event filtering (non-canonical approaches). In this paper, we present a detailed analysis and comparison of the memory requirements of canonical and non-canonical filtering algorithms. This includes a theoretical analysis of space usages as well as a verification of our theoretical results by an evaluation of a practical implementation. This practical analysis also considers time (filter) efficiency, which is the other important quality measure of filtering algorithms. By correlating the results of space and time efficiency, we conclude when to use non-canonical and canonical approaches

Two pore domain potassium channels in cerebral ischemia: a focus on K2P9.1 (TASK3, KCNK9)

BACKGROUND: Recently, members of the two-pore domain potassium channel family (K2P channels) could be shown to be involved in mechanisms contributing to neuronal damage after cerebral ischemia. K2P3.1-/- animals showed larger infarct volumes and a worse functional outcome following experimentally induced ischemic stroke. Here, we question the role of the closely related K2P channel K2P9.1. METHODS: We combine electrophysiological recordings in brain-slice preparations of wildtype and K2P9.1-/- mice with an in vivo model of cerebral ischemia (transient middle cerebral artery occlusion (tMCAO)) to depict a functional impact of K2P9.1 in stroke formation. RESULTS: Patch-clamp recordings reveal that currents mediated through K2P9.1 can be obtained in slice preparations of the dorsal lateral geniculate nucleus (dLGN) as a model of central nervous relay neurons. Current characteristics are indicative of K2P9.1 as they display an increase upon removal of extracellular divalent cations, an outward rectification and a reversal potential close to the potassium equilibrium potential. Lowering extracellular pH values from 7.35 to 6.0 showed comparable current reductions in neurons from wildtype and K2P9.1-/- mice (68.31 +/- 9.80% and 69.92 +/- 11.65%, respectively). These results could be translated in an in vivo model of cerebral ischemia where infarct volumes and functional outcomes showed a none significant tendency towards smaller infarct volumes in K2P9.1-/- animals compared to wildtype mice 24 hours after 60 min of tMCAO induction (60.50 +/- 17.31 mm3 and 47.10 +/- 19.26 mm3, respectively). CONCLUSIONS: Together with findings from earlier studies on K2P2.1-/- and K2P3.1-/- mice, the results of the present study on K2P9.1-/- mice indicate a differential contribution of K2P channel subtypes to the diverse and complex in vivo effects in rodent models of cerebral ischemia