A framework for multidimensional indexes on distributed and highly-available data stores

No-relational databases are nowadays a common solution when dealing with a huge data set and massive query workload. These systems have been redesigned from scratch in order to achieve scalability and availability at the cost of providing only a reduce set of low-level functionality, thus forcing the client application to implement complex logic. As a solution, our research group developed Hecuba, a set of tools and interfaces, which aims to facilitate developers with an efficient and painless interaction with non-relational technologies. This paper presents a part of Hecuba related to a particular missing feature: multidimensional indexing. Our work focuses on the design of architectures and the algorithms for providing multidimensional indexing on a distributed database without compromising scalability and availability

Hecuba: NoSql made easy

Non-relational databases are nowadays a common solution when dealing with huge data set and massive query work load. These systems have been redesigned from scratch in order to achieve scalability and availability at the cost of providing only a reduce set of low-level functionality, thus forcing the client application to take care of complex logics. As a solution, our research group developed Hecuba, a set of tools and interfaces, which aims to facilitate programmers with an efficient and easy interaction with non-relational technologies

Materials assessment: a shared responsibility among teachers and students

This article focuses on the development of a small-scale research project implemented in a public school in Bogotá, Colombia with a group of fourth graders who study English as a foreign language. The main goal of this research is to determine the criteria my fourth graders use when assessing the worksheets I provided them with in the English class. The data collection techniques that support the proposal are questionnaires, semi-open interviews, and the teacher’s journal. This study prompted a more collaborative environment among teacher and students regarding a basic activity of the curriculum as the materials used in class. Finally, this paper emphasizes the importance of creating classrooms that are more democratic to enrich the educational process. Key words: Materials assessment, evaluation, assessment, democratic classrooms, English innovation, foreign language innovation, curriculum Este artículo se centra en el desarrollo de un proyecto de investigación a pequeña escala implementado en un colegio público en Bogotá, Colombia con un grupo de cuarto de primaria que estudia inglés como lengua extranjera. El principal fin de esta investigación es determinar el criterio usado por mis estudiantes de cuarto de primaria cuando evalúan los talleres que yo diseño para la clase de inglés. Las técnicas de recolección de datos que soportan esta propuesta son cuestionarios, entrevistas semiabiertas, y el diario del profesor como fuente secundaria. Este estudio promovió un ambiente de mayor diálogo entre profesor y estudiantes, teniendo en cuenta una actividad básica del currículo como son los materiales usados en clase. Finalmente, este trabajo enfatiza en la importancia de crear salones más democráticos para enriquecer el proceso educativo. Palabras claves: Evaluación de materiales, evaluación, seguimiento, salones democráticos, innovación-inglés, innovación-lengua extranjera, currícul

Mejora del rendimiento de las aplicaciones Java usando cooperación entre el sistema operativo y la máquina virtual de Java

El uso de los entornos virtualizados de ejecución se ha extendido a todos los ámbitos y, en particular, se está utilizando para el desarrollo y la ejecución de aplicaciones con un alto consumo de recursos. Por lo tanto, se hace necesario evaluar si estas plataformas ofrecen un rendimiento adecuado para este tipo de programas y si es posible aprovechar las características de estas plataformas para favorecer su ejecución.El objetivo principal de este trabajo ha sido ha sido demostrar que es posible explotar las características de los entornos virtualizados de ejecución para ofrecer a los programas una gestión de recursos que se adapte mejor a sus características.En este trabajo demostramos que el modelo de ejecución de este tipo de entornos, basado en la ejecución sobre máquinas virtuales, ofrece una nueva oportunidad para implementar una gestión específica de recursos, que permite mejorar el rendimiento de los programas sin renunciar a las numerosas ventajas de este tipo de plataformas como, por ejemplo, una portabilidad total del código de los programas.Para demostrar los beneficios de esta estrategia hemos seleccionado como caso de estudio la gestión del recurso memoria para los programas de cálculo científico en el entorno de ejecución de Java. Después de un análisis detallado de la influencia que tiene la gestión de memoria sobre este tipo de programas, hemos visto que añadir en el entorno de ejecución una política de prefetch de páginas que se adapte al comportamiento de los programas es una posible vía para mejorar su rendimiento.Por este motivo, hemos analizado detalladamente los requerimientos que debe cumplir esta política y cómo repartir las tareas entre los diferentes componentes del entorno de ejecución de Java para cumplir estos requerimientos.Como consecuencia, hemos diseñado una política de prefetch basada en la cooperación entre la máquina virtual y el sistema operativo. En nuestra propuesta, por un lado, las decisiones de prefetch se llevan a cabo utilizando todo el conocimiento que la máquina virtual tiene sobre el comportamiento dinámico de los programas y el conocimiento que el sistema operativo tiene sobre las condiciones de ejecución. Por otro lado, el encargado de llevar a cabo las decisiones de gestión es el sistema operativo, lo que garantiza la fiabilidad de la máquina.Además, esta estrategia es totalmente transparente al programador y al usuario, respetando el paradigma de portabilidad de los entornos de ejecución virtualizados.Hemos implementado y evaluado esta estrategia para demostrar los beneficios que ofrece al tipo de programas seleccionado y, aunque estos beneficios dependen de las características del programa, la mejora del rendimiento ha alcanzado hasta un 40% si se compara con el rendimiento obtenido sobre el entorno original de ejecución.Postprint (published version

A compromise archive platform for monitoring infrastructures

The great advancement in the technological field has led to an explosion in the amount of generated data. Many different sectors have understood the opportunity that acquiring, storing, and analyzing further information means, which has led to a broad proliferation of measurement devices. Those sensors’ typical job is to monitor the state of the enterprise ecosystem, which can range from a traditional factory, to a commercial mall, or even to the largest experiment on Earth[1]. Big enterprises (BEs) are building their own big data architectures, usually made out of a combination of several state-of-the-art technologies. Finding new interesting data to measure, store and analyze, has become a daily process in the industrial field. However, small and medium-sized enterprises (SMEs) usually lack the resources needed to build those data handling architectures, not just in terms of hardware resources, but also in terms of contracting personnel who can master all those rapidly evolving technologies. Our research tries to adapt two world-wide-used technologies into a single but elastic and moldable one, by tuning them, to offer an alternative and efficient solution for this very specific, but common, scenario

Introducing polyglot-based data-flow awareness to time-series data stores

The rising interest in extracting value from data has led to a broad proliferation of monitoring infrastructures, most notably composed by sensors, intended to collect this new oil. Thus, gathering data has become fundamental for a great number of applications, such as predictive maintenance techniques or anomaly detection algorithms. However, before data can be refined into insights and knowledge, it has to be efficiently stored and prepared for its later retrieval. As a consequence of this sensor and IoT boom, Time-Series databases (TSDB), designed to manage sensor data, became the fastest-growing database category since 2019. Here we propose a holistic approach intended to improve TSDB’s performance and efficiency. More precisely, we introduce and evaluate a novel polyglot-based approximation, aimed to tailor the data store, not only to time-series data –as it is done conventionally– but also to the data flow itself: From its ingestion, until its retrieval. In order to evaluate the approach, we materialize it in an alternative implementation of NagareDB, a resource-efficient time-series database, based on MongoDB, in turn, the most popular NoSQL storage solution. After implementing our approach into the database, we observe a global speed up, solving queries up to 12 times faster than MongoDB’s recently launched Time-series capability, as well as generally outperforming InfluxDB, the most popular time-series database. Our polyglot-based data-flow aware solution can ingest data more than two times faster than MongoDB, InfluxDB, and NagareDB’s original implementation, while using the same disk space as InfluxDB, and half of the requested by MongoDB.This research was partly supported by the Spanish Ministry of Science and Innovation (contract PID2019-107255GB) and by the Generalitat de Catalunya (contract 2017-SGR-1414).Peer ReviewedPostprint (published version

A holistic scalability strategy for time series databases following cascading polyglot persistence

Time series databases aim to handle big amounts of data in a fast way, both when introducing new data to the system, and when retrieving it later on. However, depending on the scenario in which these databases participate, reducing the number of requested resources becomes a further requirement. Following this goal, NagareDB and its Cascading Polyglot Persistence approach were born. They were not just intended to provide a fast time series solution, but also to find a great cost-efficiency balance. However, although they provided outstanding results, they lacked a natural way of scaling out in a cluster fashion. Consequently, monolithic approaches could extract the maximum value from the solution but distributed ones had to rely on general scalability approaches. In this research, we proposed a holistic approach specially tailored for databases following Cascading Polyglot Persistence to further maximize its inherent resource-saving goals. The proposed approach reduced the cluster size by 33%, in a setup with just three ingestion nodes and up to 50% in a setup with 10 ingestion nodes. Moreover, the evaluation shows that our scaling method is able to provide efficient cluster growth, offering scalability speedups greater than 85% in comparison to a theoretically 100% perfect scaling, while also ensuring data safety via data replication.This research was partly supported by the Grant Agreement No. 857191, by the Spanish Ministry of Science and Innovation (contract PID2019-107255GB) and by the Generalitat de Catalunya (contract 2017-SGR-1414).Peer ReviewedPostprint (published version

Evaluating the benefits of key-value databases for scientific applications

The convergence of Big Data applications with High-Performance Computing requires new methodologies to store, manage and process large amounts of information. Traditional storage solutions are unable to scale and that results in complex coding strategies. For example, the brain atlas of the Human Brain Project has the challenge to process large amounts of high-resolution brain images. Given the computing needs, we study the effects of replacing a traditional storage system with a distributed Key-Value database on a cell segmentation application. The original code uses HDF5 files on GPFS through an intricate interface, imposing synchronizations. On the other hand, by using Apache Cassandra or ScyllaDB through Hecuba, the application code is greatly simplified. Thanks to the Key-Value data model, the number of synchronizations is reduced and the time dedicated to I/O scales when increasing the number of nodes.This project/research has received funding from the European Unions Horizon 2020 Framework Programme for Research and Innovation under the Speci c Grant Agreement No. 720270 (Human Brain Project SGA1) and the Speci c Grant Agreement No. 785907 (Human Brain Project SGA2). This work has also been supported by the Spanish Government (SEV2015-0493), by the Spanish Ministry of Science and Innovation (contract TIN2015-65316-P), and by Generalitat de Catalunya (contract 2017-SGR-1414).Postprint (author's final draft

Twin texts: a possibility to involve children in inquiry-oriented processes

This article reports on the experience I lived while implementing the instructional design of my Master thesis. The research proposal I am currently carrying out is primarily concerned about conflict resolution and cooperative learning in the English classroom. The proposal was developed in a public primary school in Ciudad Bolivar, Bogotá, Colombia. Besides, my participants were a group of fourth graders. The methodology used during the implementation had to do with: cooperative learning, in which learning implies co-construction. The authoring cycle that is an option for involving students in inquiry processes, and twin texts, understood as the use of two books (one fictional & one non-fictional) related to the same topic but from different perspectives. The three elements described above were interwoven along the process. To conclude, this experience helped me to recognize certain aspects regarding my professional practices: first, the importance of innovation. Second, the value of other teacher-researchers’ experiences and insights. Third, to recognize our students as owners of their learning process. Fourth, how the authoring cycle promoted cooperative learning and decreased conflicts. Finally and foremost, the value of literature as a powerful language learning resource.Este artículo reporta la experiencia que viví mientras implementaba el diseño instruccional de mi tesis de Maestría. La propuesta de investigación que estoy desarrollando actualmente tiene que ver principalmente con resolución de conflicto y aprendizaje cooperativo en la clase de inglés. La propuesta fue desarrollada en una escuela primaria pública en Ciudad Bolívar, Bogotá, Colombia. Además, mis participantes fueron un grupo de niñ@s de cuarto de primaria. La metodología usada durante la implementación tuvo que ver con aprendizaje cooperativo, en el que aprendizaje implica co-construcción. El ciclo de autoría que es una opción para involucrar a los estudiantes en procesos de investigación, y libros gemelos, entendido como el uso de dos libros (uno de ficción y otro de no- ficción) relacionados con el mismo tema pero desde diferentes perspectivas. Los tres elementos descritos antes estuvieron entretejidos a lo largo del proceso.&nbsp

Teacher voice: how is it shaped?

This article aims at being an invitation for the readers to refl ect upon the way in which our voices as teachers are shaped. My own refl ective process geared me towards the characterization of three key issues which –from my personal and professional experience- shape teacher voice. They are: the political relations of power, the curricular choices we make and their implications, and the government policies. Grounded on some Critical Pedagogy scholars, I defi ne fi rst, Critical pedagogy from my personal stand. Second, I present the defi nition of teacher voice, from different perspectives, including mine. Third, I describe and illustrate each of the three central features that may shape our voices as teachers and fi nally, I state some conclusions and pedagogical implications.Este artículo pretende ser una invitación a los lectores para que refl exionen acerca de la forma en que nuestras voces como profesor@s son formadas. Mi propio proceso de refl exión me orientó hacia la caracterización de asuntos claves que- desde mi experiencia personal y profesional- forman la voz del profesor (a). Ellos son: las relaciones políticas de poder, las elecciones curriculares que hacemos y sus implicaciones, y las políticas gubernamentales. Basada en algunos teóricos de la Pedagogía Crítica, defi no primero Pedagogía Crítica desde mi posición personal. Segundo, presento la defi nición de la voz del profesor (a) desde diferentes perspectivas, incluida la mía. Tercero, describo e ilustro cada uno de los tres rasgos centrales que pueden formar nuestra voz como profesor@s y fi nalmente, establezco algunas conclusiones e implicaciones pedagógicas