Efficient Probabilistic Subsumption Checking for Content-Based Publish/Subscribe Systems

Abstract. Efficient subsumption checking, deciding whether a subscription or publication is covered by a set of previously defined subscriptions, is of paramount importance for publish/subscribe systems. It provides the core system functionality—matching of publications to subscriber needs expressed as subscriptions—and additionally, reduces the overall system load and generated traffic since the covered subscriptions are not propagated in distributed environments. As the subsumption problem was shown previously to be co-NP complete and existing solutions typically apply pairwise comparisons to detect the subsumption relationship, we propose a ‘Monte Carlo type ’ probabilistic algorithm for the general subsumption problem. It determines whether a publication/subscription is covered by a disjunction of subscriptions in O(k md), wherek is the number of subscriptions, m is the number of distinct attributes in subscriptions, and d is the number of tests performed to answer a subsumption question. The probability of error is problem-specific and typically very small, and sets an upper bound on d. Our experimental results show significant gains in term of subscription set reduction which has favorable impact on the overall system performance as it reduces the total computational costs and networking traffic. Furthermore, the expected theoretical bounds underestimate algorithm performance because it performs much better in practice due to introduced optimizations, and is adequate for fast forwarding of subscriptions in case of high subscription rate.

Query Driven Operator Placement for Complex Event Detection over Data Streams

We consider the problem of efficiently processing subscription queries over data streams in large-scale interconnected sensor networks. We propose a scalable algorithm for distributed data stream processing, applicable on top of any platform granting access to interconnected sensor networks. We make use of a probabilistic algorithm to check whether subscriptions are subsumed by other subscriptions and thus can be pruned for more efficient processing. Our proposed methods are query driven, hence do not replicate data streams, but intelligently place join operators inside the global network of sources. We show by a performance evaluation using real world sensor data the suitability of our approach

Community-Aware Event Dissemination

This paper presents a distributed algorithm to disseminate events in a publish/subscribe system, where processes publish events of certain topics, organized in a hierarchy, and expect events of topics they subscribed to. Every topic defines a dynamic notion of ``community'', gathering the processes which publish on that topic or subscribe to it. Our algorithm is completely decentralized (no brokers), yet does not require from any process to ever receive, store or forward, events from a community it is not part of. We order the communities according to the topic inclusion relationships to efficiently manage the flow of information within, and between the communities, as well as limit the memory consumption of each process. Processes can control, for each of their communities, the trade-off between the message complexity and the reliability of event dissemination. We convey this trade-off through analysis, simulations and measurements obtained with a full implementation of our algorithm

Fast Probabilistic Subsumption Checking for Publish/Subscribe Systems

Efficient subsumption checking, deciding whether a subscription or publication is subsumed (covered) by a set of previously defined subscriptions, is of paramount importance for publish/subscribe systems. It provides the core system functionality, and additionally, reduces the overall system load and generated traffic in distributed environments. As the deterministic solution was shown previously to be co-NP complete and existing solutions typically employ costly pairwise comparisons to detect the subsumption relationship, we propose a probabilistic algorithm for the general subsumption problem. It efficiently determines whether a publication/subscription is covered by a disjunction of subscriptions in $O(k~m~d)$, where $k$ is the number of subscriptions, $m$ is the number of distinct attributes in subscriptions, and $d$ is the number of tests performed to answer a subsumption question. The probability of error is problem specific and typically very small, and determines an upper bound on $d$ in polynomial time prior to the algorithm execution. Our experimental results demonstrate the algorithm performs even better in practice due to introduced optimizations, and is adequate for fast forwarding of publications/subscriptions, especially in resource scarce environments, e.g. sensor networks

HIGH SCHOOL FEMALE STUDENTS’ SATISFACTION DEGREE AFTER PRACTICING SPECIFIC AQUAGYM PROGRAMS AS AN EXTRACURRICULAR ACTIVITY

Introduction. The aquatic environment offers numerous exercise opportunities with a focus on achieving sports performance, as well as a number of beneficial effects compared to the terrestrial environment. The biological adaptation to aquagym-specific exercises, supported by the physical properties of the aquatic environment, is the response of the body to physical stimuli leading to ameliorative changes in body functions. The novelty of the activity and the relative ease of this form of physical exercise stimulated and motivated the female participants in an aquagym program carried out in the 1st semester of the school year 2021-2022. Objective. Our statement is supported by the results obtained from carrying out a satisfaction survey which aimed to highlight the impact of aquatic recreational activities, namely aquagym, and the effectiveness of the means selected in the operational programs on motor and functional capacity. Materials and Methods. The study included 37 high school female students, aged 16-17, from “Carol I” National College in Craiova. In order to optimize the students’ motor skills, an aquagym-specific program of exercises was developed and carried out along 12 sessions of 50 minutes each. At the end of the program, an opinion questionnaire was administered addressing high school female students’ degree of satisfaction with the content of aquagym sessions. Results. The application of the questionnaire-based satisfaction survey highlighted the advantages of practicing aquagym ranging from bio-motor benefits, such as the increase in flexibility, balance and muscular strength, to aspects outlining the improvement in some components of quality of life. The result of this survey confirms that the aquagym program was appreciated by the students who became aware of the positive effects obtained. Conclusions. Our students’ participation in aquagym-specific programs revealed the need to improve the educational offer of the school subject Physical Education and to harmonize the contents of the classes with students’ options. The analysis of the survey findings shows that the students rated the recreational content higher than the effects on motor skills and, surprisingly, a very small percentage of the students appreciated the effects on body shaping. Received 2022 April 27; Revised 2022 July 20; Accepted 2022 July 21; Available online 2022 June 30; Available print 2022 August 30. REZUMAT. Gradul de satisfacție al elevelor de liceu după practicarea programelor specifice de aquagym ca activitate extracurriculară. Introducere. Mediul acvatic oferă numeroase oportunități de exerciții fizice, cu accent pe obținerea de performanțe sportive, precum și o serie de efecte benefice în comparație cu cele oferite de mediul terestru. Adaptarea biologică la exercițiile specifice aquagym-ului, susținută de proprietățile fizice ale mediului acvatic, este răspunsul organismului la stimuli fizici care provoacă modificări ameliorative ale funcțiilor corpului. Noutatea activității și relativa facilitate a acestei forme de practicare a exercițiului fizic a stimulat și motivat participantele la un program de aqugym, desfășurat în anul școlar 2021-2022, semestrul I. Obiectiv. Afirmația noastră este susținută de rezultatele obținute în urma aplicării unui chestionar de satisfacție care și-a propus să evidențieze impactul activității ludico-recreative acvatice, respectiv a aquagym-ului și eficiența mijloacelor selecționate în cadrul programelor operaționale asupra capacității motrice și funcționale. Materiale și metode. Studiul a inclus 37 de eleve de liceu cu vârsta cuprinsă între 16-17 ani de la Colegiul Național „Carol I” Craiova. Pentru optimizarea capacității motrice a elevelor s-a alcătuit un program de exerciții specifice aquagym-ului, desfășurat timp de 12 ședințe, cu o durată de 50 de minute. La sfârșitul programului a fost aplicat un chestionar de opinie vizând gradul de satisfacție al elevelor de liceu cu privire la conținutul ședințelor de aquagym. Rezultate. Aplicarea chestionarului de satisfacție a evidențiat avantajele practicării aquagym-ului pornind de la beneficiile bio-motrice, cum ar fi creșterea flexibilității, echilibrului și forței musculare, către aspecte ce conturează îmbunătățirea unor componente ale calității vieții. Rezultatul prezentei anchete confirmă faptul că programul de aquagym a fost apreciat de eleve, care, au conștientizat efectele pozitive obținute. Concluzii. Participarea la programele specifice aquagym-ului a evidențiat nevoia de îmbunătățire a ofertei educaționale la disciplina educație fizică și a racordării conținuturilor lecțiilor la opțiunile elevilor. Din analiza rezultatelor chestionarului se remarcă faptul că elevele apreciază mai mult conținutul recreativ, mai puțin efectele asupra capacității motrice și în mod surprinzător, un procent foarte mic au apreciat efectele asupra modelării corporale. Cuvinte cheie: program aquagym, capacitate motrică, sisteme de acționare, satisfactie, elevele de lice

Height and body-mass index trajectories of school-aged children and adolescents from 1985 to 2019 in 200 countries and territories: a pooled analysis of 2181 population-based studies with 65 million participants

Summary Background Comparable global data on health and nutrition of school-aged children and adolescents are scarce. We aimed to estimate age trajectories and time trends in mean height and mean body-mass index (BMI), which measures weight gain beyond what is expected from height gain, for school-aged children and adolescents. Methods For this pooled analysis, we used a database of cardiometabolic risk factors collated by the Non-Communicable Disease Risk Factor Collaboration. We applied a Bayesian hierarchical model to estimate trends from 1985 to 2019 in mean height and mean BMI in 1-year age groups for ages 5–19 years. The model allowed for non-linear changes over time in mean height and mean BMI and for non-linear changes with age of children and adolescents, including periods of rapid growth during adolescence. Findings We pooled data from 2181 population-based studies, with measurements of height and weight in 65 million participants in 200 countries and territories. In 2019, we estimated a difference of 20 cm or higher in mean height of 19-year-old adolescents between countries with the tallest populations (the Netherlands, Montenegro, Estonia, and Bosnia and Herzegovina for boys; and the Netherlands, Montenegro, Denmark, and Iceland for girls) and those with the shortest populations (Timor-Leste, Laos, Solomon Islands, and Papua New Guinea for boys; and Guatemala, Bangladesh, Nepal, and Timor-Leste for girls). In the same year, the difference between the highest mean BMI (in Pacific island countries, Kuwait, Bahrain, The Bahamas, Chile, the USA, and New Zealand for both boys and girls and in South Africa for girls) and lowest mean BMI (in India, Bangladesh, Timor-Leste, Ethiopia, and Chad for boys and girls; and in Japan and Romania for girls) was approximately 9–10 kg/m2. In some countries, children aged 5 years started with healthier height or BMI than the global median and, in some cases, as healthy as the best performing countries, but they became progressively less healthy compared with their comparators as they grew older by not growing as tall (eg, boys in Austria and Barbados, and girls in Belgium and Puerto Rico) or gaining too much weight for their height (eg, girls and boys in Kuwait, Bahrain, Fiji, Jamaica, and Mexico; and girls in South Africa and New Zealand). In other countries, growing children overtook the height of their comparators (eg, Latvia, Czech Republic, Morocco, and Iran) or curbed their weight gain (eg, Italy, France, and Croatia) in late childhood and adolescence. When changes in both height and BMI were considered, girls in South Korea, Vietnam, Saudi Arabia, Turkey, and some central Asian countries (eg, Armenia and Azerbaijan), and boys in central and western Europe (eg, Portugal, Denmark, Poland, and Montenegro) had the healthiest changes in anthropometric status over the past 3·5 decades because, compared with children and adolescents in other countries, they had a much larger gain in height than they did in BMI. The unhealthiest changes—gaining too little height, too much weight for their height compared with children in other countries, or both—occurred in many countries in sub-Saharan Africa, New Zealand, and the USA for boys and girls; in Malaysia and some Pacific island nations for boys; and in Mexico for girls. Interpretation The height and BMI trajectories over age and time of school-aged children and adolescents are highly variable across countries, which indicates heterogeneous nutritional quality and lifelong health advantages and risks

A Publish/Subscribe Approach to Processing Continuous Queries over Sensor Streams

With technological advances, the sources of available information have become more and more diverse. Recently, a new source of information has gained growing importance: sensor data. Sensors are devices sensing their environment in various ways and reporting in general a numeric result. A sensor continuously reports values, thus the flow of information is also continuous, like a stream. As the field has developed, the usage paradigm has shifted from stand-alone sensors to interconnected sensors, or sensor networks. Sensors became more complex, generating larger quantities of data and having wireless communication modules for transmitting their data. Initially, data from sensor networks was first stored, and then processed. Thus, classical database technologies could be used. However, the focus has soon shifted towards reacting to sensor data in real time. A user query reacting in real time to a stream of data is called a continuous query, and to answer such a query requires that it is continuously processed, as new values appear in the sensor stream. As sensor networks and sensor based applications become more popular, users identified the need to query sensor data pertaining to different sensor networks. This setting, of interconnected sensor networks, consists of more powerful computational devices, connected with a wired communication, which can process and relay sensor data. Users can launch queries at any node to query sensor events coming from any part of the interconnected network. In this setting, the number of data sources (sensors) is orders of magnitude smaller than the number of user queries, which themselves are orders of magnitude smaller than the full content of the (sensor) data streams, and the communication becomes by far the greatest communication bottleneck. In this thesis, we present our research for reducing communication cost generated by applications accessing large scale interconnected sensor networks. Our first contribution is a probabilistic algorithm for detecting and exploiting subsumption of queries over correlated data sources. This technique reduces the communication traffic generated by query forwarding in an interconnected sensor network, by filtering out queries subsumed by a set of existing queries. In addition, this reduces the number of results that need to be transmitted. We propose an efficient forwarding algorithm of the elements of the result sets, by employing a publish/subscribe data dissemination. To support the general setting of distributed data sources in an interconnected sensor network, we propose a Filter-Split-Forward approach that adapts set subsumption to the case of join queries over distributed data sources. We base our approach on the concept of filter-split-forward phases for efficient query filtering and placement inside the network, and an efficient, publish/subscribe forwarding of matching events. We also propose distributed adaptations of state of the art solutions for continuous query processing over multiple data sources. We adapt these techniques to require only local interactions between nodes, without relying on global knowledge or a centralized server. We show how our approach achieves lower traffic through query subsumption and efficient event dissemination. In many applications using sensor data, users are only interested in the most relevant events. To that end, we present our solutions for processing top-k queries over distributed sensor data streams in the presence of query subsumption. We analyze the impact of query subsumption on top-k processing. We propose different strategies for incorporating query subsumption into top-k processing, in order to obtain sufficiently accurate result sets, while keeping network traffic low. We show that the best tradeoff is achieved by updating throughout the network the values of k for the queries resulting from splitting a query between nodes and also for the set of queries subsuming a query. By this work we contribute a framework for increasing the efficiency of continuous query processing over distributed data sources for a wide range of applications, such as environmental and living spaces monitoring, network and traffic monitoring, and in general for all sensor enhanced monitoring applications