Distributed Query Monitoring through Convex Analysis: Towards Composable Safe Zones

Continuous tracking of complex data analytics queries over high-speed distributed streams is becoming increasingly important. Query tracking can be reduced to continuous monitoring of a condition over the global stream. Communication-efficient monitoring relies on locally processing stream data at the sites where it is generated, by deriving site-local conditions which collectively guarantee the global condition. Recently proposed geometric techniques offer a generic approach for splitting an arbitrary global condition into local geometric monitoring constraints (known as "Safe Zones"); still, their application to various problem domains has so far been based on heuristics and lacking a principled, compositional methodology. In this paper, we present the first known formal results on the difficult problem of effective Safe Zone (SZ) design for complex query monitoring over distributed streams. Exploiting tools from convex analysis, our approach relies on an algebraic representation of SZs which allows us to: (1) Formally define the notion of a "good" SZ for distributed monitoring problems; and, most importantly, (2) Tackle and solve the important problem of systematically composing SZs for monitored conditions expressed as Boolean formulas over simpler conditions (for which SZs are known); furthermore, we prove that, under broad assumptions, the composed SZ is good if the component SZs are good. Our results are, therefore, a first step towards a principled compositional solution to SZ design for distributed query monitoring. Finally, we discuss a number of important applications for our SZ design algorithms, also demonstrating how earlier geometric techniques can be seen as special cases of our framework

Histograms and Wavelets on Probabilistic Data

There is a growing realization that uncertain information is a first-class citizen in modern database management. As such, we need techniques to correctly and efficiently process uncertain data in database systems. In particular, data reduction techniques that can produce concise, accurate synopses of large probabilistic relations are crucial. Similar to their deterministic relation counterparts, such compact probabilistic data synopses can form the foundation for human understanding and interactive data exploration, probabilistic query planning and optimization, and fast approximate query processing in probabilistic database systems. In this paper, we introduce definitions and algorithms for building histogram- and wavelet-based synopses on probabilistic data. The core problem is to choose a set of histogram bucket boundaries or wavelet coefficients to optimize the accuracy of the approximate representation of a collection of probabilistic tuples under a given error metric. For a variety of different error metrics, we devise efficient algorithms that construct optimal or near optimal B-term histogram and wavelet synopses. This requires careful analysis of the structure of the probability distributions, and novel extensions of known dynamic-programming-based techniques for the deterministic domain. Our experiments show that this approach clearly outperforms simple ideas, such as building summaries for samples drawn from the data distribution, while taking equal or less time

PERCEPTIONS ON WHICH SOCIAL NETWORKING TOOLS ARE USEFUL FOR TEACHERS’ PROFESSIONAL DEVELOPMENT

Teachers are expected to be able to keep up with the technological development in the classroom. Integrating ICT into teaching is a complex process and they may encounter a number of difficulties. They seek opportunities for professional development, so that they can meet the needs of students leading to recognition as a “reform-minded” educator. Social networking/WEB2.0 which is the technology connecting people is providing new opportunities for professional development by assisting to remain current on skills important for teachers’ role. Aim of our research is to study, for the specific professional category of school teachers, which are the professional skills which can be strengthened through social networking and which tools are the most appropriate for this goal. Based on a collection of information from various sources we present a series of conclusions which can be the basis for the design of training programs on how to effectively use social networking.  Article visualizations

OBSTACLES ON THE EFFECTIVE USE OF SOCIAL NETWORKING TOOLS FOR TEACHERS’ PROFESSIONAL DEVELOPMENT AND THE TRAINING NEEDS TO DEAL WITH THEM

Social networking /WEB 2.0 is the technology to support connecting people in various ways. The arise of WEB 2.0 allowed users to enhance their actions when accessing the internet not only for searching information but above all to interact, collaborate, and share content. For the specific showcase of school teachers, WEB 2.0 is providing new opportunities to build and gain professional development by assisting them to remain current on skills and issues important for a professional role. Aim of the presented work, it to build on our previous research on which specific tools are considered as the most useful for teachers’ professional development and which are the perceptions of teachers on them, in order to identify the obstacles and drawbacks to their effective utilization, leading to the proposition of a core training program tailored to the teachers’ needs.  Article visualizations