Confidence: dependencies and their critical role in fostering user acceptance in pervasive applications

Pervasive computing offers new scenarios where users are surrounded by invisible and proactive technology making smart spaces. Although the utility and power of solutions developed using this computer paradigm are proved, there are unresolved problems that hinder their acceptance and inclusion in our private life. Users have problems understanding the operations of a pervasive computing solution, and therefore they should trust that the solution works properly and according to their expectations. Nevertheless, the concept of trust is already framed in a specific use within the ecosystem of applications that can populate a smart space. To take this concept of trust to the whole space, we propose to study and define the concept of confidence. In contrast to the concept of trust, confidence has deeper psychological implications.

An energy-efficient strategy for combined RSS-PDR indoor localization

We propose an optimization-based framework to minimize the energy consumption in a sensor network when using an indoor localization system based on the combination of received signal strength (RSS) and pedestrian dead reckoning (PDR). The objective is to find the RSS localization frequency and the number of RSS measurements used at each localization round that jointly minimize the total consumed energy, while ensuring at the same time a desired accuracy in the localization result. The optimization approach leverages practical models to predict the localization error and the overall energy consumption for combined RSS-PDR localization systems. The performance of the proposed strategy is assessed through simulation, showing energy savings with respect to other approaches while guaranteeing a target accuracy.

Semantic middleware development for the Internet of Things

After the extraordinary spread of the World Wide Web during the last fifteen years, engineers and developers are pushing now the Internet to its next border. A new conception in computer science and networks communication has been burgeoning during roughly the last decade: a world where most of the computers of the future will be extremely downsized, to the point that they will look like dust at its most advanced prototypes. In this vision, every single element of our ���real��� world has an intelligent tag that carries all their relevant data, effectively mapping the ���real��� world into a ���virtual��� one, where all the electronically augmented objects are present, can interact among them and influence with their behaviour that of the other objects, or even the behaviour of a final human user. This is the vision of the Internet of the Future, which also draws ideas of several novel tendencies in computer science and networking, as pervasive computing and the Internet of Things. As it has happened before, materializing a new paradigm that changes the way entities interrelate in this new environment has proved to be a goal full of challenges in the way. Right now the situation is exciting, with a plethora of new developments, proposals and models sprouting every time, often in an uncoordinated, decentralised manner away from any standardization, resembling somehow the status quo of the first developments of advanced computer networking, back in the 60s and the 70s. Usually, a system designed after the Internet of the Future will consist of one or several final user devices attached to these final users, a network ���often a Wireless Sensor Network- charged with the task of collecting data for the final user devices, and sometimes a base station sending the data for its further processing to less hardware-constrained computers. When implementing a system designed with the Internet of the Future as a pattern, issues, and more specifically, limitations, that must be faced are numerous: lack of standards for platforms and protocols, processing bottlenecks, low battery lifetime, etc. One of the main objectives of this project is presenting a functional model of how a system based on the paradigms linked to the Internet of the Future works, overcoming some of the difficulties that can be expected and showing a model for a middleware architecture specifically designed for a pervasive, ubiquitous system. This Final Degree Dissertation is divided into several parts. Beginning with an Introduction to the main topics and concepts of this new model, a State of the Art is offered so as to provide a technological background. After that, an example of a semantic and service-oriented middleware is shown; later, a system built by means of this semantic and service-oriented middleware, and other components, is developed, justifying its placement in a particular scenario, describing it and analysing the data obtained from it. Finally, the conclusions inferred from this system and future works that would be good to be tackled are mentioned as well. RESUMEN Tras el extraordinario desarrollo de la Web durante los ��ltimos quince a��os, ingenieros y desarrolladores empujan Internet hacia su siguiente frontera. Una nueva concepci��n en la computaci��n y la comunicaci��n a trav��s de las redes ha estado floreciendo durante la ��ltima d��cada; un mundo donde la mayor��a de los ordenadores del futuro ser��n extremadamente reducidas de tama��o, hasta el punto que parecer��n polvo en sus m��s avanzado prototipos. En esta visi��n, cada uno de los elementos de nuestro mundo ���real��� tiene una etiqueta inteligente que porta sus datos relevantes, mapeando de manera efectiva el mundo ���real��� en uno ���virtual���, donde todos los objetos electr��nicamente aumentados est��n presentes, pueden interactuar entre ellos e influenciar con su comportamiento el de los otros, o incluso el comportamiento del usuario final humano. ��sta es la visi��n del Internet del Futuro, que tambi��n toma ideas de varias tendencias nuevas en las ciencias de la computaci��n y las redes de ordenadores, como la computaci��n omnipresente y el Internet de las Cosas. Como ha sucedido antes, materializar un nuevo paradigma que cambia la manera en que las entidades se interrelacionan en este nuevo entorno ha demostrado ser una meta llena de retos en el camino. Ahora mismo la situaci��n es emocionante, con una pl��tora de nuevos desarrollos, propuestas y modelos brotando todo el rato, a menudo de una manera descoordinada y descentralizada lejos de cualquier estandarizaci��n, recordando de alguna manera el estado de cosas de los primeros desarrollos de redes de ordenadores avanzadas, all�� por los a��os 60 y 70. Normalmente, un sistema dise��ado con el Internet del futuro como modelo consistir�� en uno o varios dispositivos para usuario final sujetos a estos usuarios finales, una red ���a menudo, una red de sensores inal��mbricos- encargada de recolectar datos para los dispositivos de usuario final, y a veces una estaci��n base enviando los datos para su consiguiente procesado en ordenadores menos limitados en hardware. Al implementar un sistema dise��ado con el Internet del futuro como patr��n, los problemas, y m��s espec��ficamente, las limitaciones que deben enfrentarse son numerosas: falta de est��ndares para plataformas y protocolos, cuellos de botella en el procesado, bajo tiempo de vida de las bater��as, etc. Uno de los principales objetivos de este Proyecto Fin de Carrera es presentar un modelo funcional de c��mo trabaja un sistema basado en los paradigmas relacionados al Internet del futuro, superando algunas de las dificultades que pueden esperarse y mostrando un modelo de una arquitectura middleware espec��ficamente dise��ado para un sistema omnipresente y ubicuo. Este Proyecto Fin de Carrera est�� dividido en varias partes. Empezando por una introducci��n a los principales temas y conceptos de este modelo, un estado del arte es ofrecido para proveer un trasfondo tecnol��gico. Despu��s de eso, se muestra un ejemplo de middleware sem��ntico orientado a servicios; despu��s, se desarrolla un sistema construido por medio de este middleware sem��ntico orientado a servicios, justificando su localizaci��n en un escenario particular, describi��ndolo y analizando los datos obtenidos de ��l. Finalmente, las conclusiones extra��das de este sistema y las futuras tareas que ser��a bueno tratar tambi��n son mencionadas.

High-level languages for small devices: A case study

In this paper we study, through a concrete case, the feasibility of using a high-level, general-purpose logic language in the design and implementation of applications targeting wearable computers. The case study is a "sound spatializer" which, given real-time sign��is for monaural audio and heading, generates stereo sound which appears to come from a position in space. The use of advanced compile-time transformations and optimizations made it possible to execute code written in a clear style without ef��ciency or architectural concerns on the target device, while meeting strict existing time and memory constraints. The final executable compares favorably with a similar implementation written in C. We believe that this case is representative of a wider class of common pervasive computing applications, and that the techniques we show here can be put to good use in a range of scenarios. This points to the possibility of applying high-level languages, with their associated flexibility, conciseness, ability to be automatically parallelized, sophisticated compile-time tools for analysis and verification, etc., to the embedded systems field without paying an unnecessary performance penalty.

ICTD Work, Plus mFeel : improving communication in resource-poor settings

This issue's Works-In-Progress department has four entries related to the issue's theme, Information and Communication Technologies for Development (ICTD). They are ���Sustainable ICT in Agricultural Value Chains���, ���Measuring Social Inclusion in Primary Schools���, ���An Architecture for Green Mobile Computation���, and ���Improving Communication in Resource-Poor Settings���. A fifth entry, ���mFeel: An Affective Mobile System���, covers the mFeel mobile system, which combines context awareness with affective and cognitive techniques.

A Development Methodology to Facilitate the Integration of Smart Spaces into the Web of Things

How to create or integrate large Smart Spaces (considered as mash-ups of sensors and actuators) into the paradigm of ?Web of Things? has been the motivation of many recent works. A cutting-edge approach deals with developing and deploying web-enabled embedded devices with two major objectives: 1) to integrate sensor and actuator technologies into everyday objects, and 2) to allow a diversity of devices to plug to Internet. Currently, developers who want to use this Internet-oriented approach need have solid understanding about sensorial platforms and semantic technologies. In this paper we propose a Resource-Oriented and Ontology-Driven Development (ROOD) methodology, based on Model Driven Architecture (MDA), to facilitate to any developer the development and deployment of Smart Spaces. Early evaluations of the ROOD methodology have been successfully accomplished through a partial deployment of a Smart Hotel.

A Novel Approach to Context-Aware Content-Based Middleware

La computaci��n ubicua est�� extendiendo su aplicaci��n desde entornos espec��ficos hacia el uso cotidiano; el Internet de las cosas (IoT, en ingl��s) es el ejemplo m��s brillante de su aplicaci��n y de la complejidad intr��nseca que tiene, en comparaci��n con el cl��sico desarrollo de aplicaciones. La principal caracter��stica que diferencia la computaci��n ubicua de los otros tipos est�� en como se emplea la informaci��n de contexto. Las aplicaciones cl��sicas no usan en absoluto la informaci��n de contexto o usan s��lo una peque��a parte de ella, integr��ndola de una forma ad hoc con una implementaci��n espec��fica para la aplicaci��n. La motivaci��n de este tratamiento particular se tiene que buscar en la dificultad de compartir el contexto con otras aplicaciones. En realidad lo que es informaci��n de contexto depende del tipo de aplicaci��n: por poner un ejemplo, para un editor de im��genes, la imagen es la informaci��n y sus metadatos, tales como la hora de grabaci��n o los ajustes de la c��mara, son el contexto, mientras que para el sistema de ficheros la imagen junto con los ajustes de c��mara son la informaci��n, y el contexto es representado por los metadatos externos al fichero como la fecha de modificaci��n o la de ��ltimo acceso. Esto significa que es dif��cil compartir la informaci��n de contexto, y la presencia de un middleware de comunicaci��n que soporte el contexto de forma expl��cita simplifica el desarrollo de aplicaciones para computaci��n ubicua. Al mismo tiempo el uso del contexto no tiene que ser obligatorio, porque si no se perder��a la compatibilidad con las aplicaciones que no lo usan, convirtiendo as�� dicho middleware en un middleware de contexto. SilboPS, que es nuestra implementaci��n de un sistema publicador/subscriptor basado en contenido e inspirado en SIENA [11, 9], resuelve dicho problema extendiendo el paradigma con dos elementos: el Contexto y la Funci��n de Contexto. El contexto representa la informaci��n contextual propiamente dicha del mensaje por enviar o aquella requerida por el subscriptor para recibir notificaciones, mientras la funci��n de contexto se eval��a usando el contexto del publicador y del subscriptor. Esto permite desacoplar la l��gica de gesti��n del contexto de aquella de la funci��n de contexto, incrementando de esta forma la flexibilidad de la comunicaci��n entre varias aplicaciones. De hecho, al utilizar por defecto un contexto vac��o, las aplicaciones cl��sicas y las que manejan el contexto pueden usar el mismo SilboPS, resolviendo de esta forma la incompatibilidad entre las dos categor��as. En cualquier caso la posible incompatibilidad sem��ntica sigue existiendo ya que depende de la interpretaci��n que cada aplicaci��n hace de los datos y no puede ser solucionada por una tercera parte agn��stica. El entorno IoT conlleva retos no s��lo de contexto, sino tambi��n de escalabilidad. La cantidad de sensores, el volumen de datos que producen y la cantidad de aplicaciones que podr��an estar interesadas en manipular esos datos est�� en continuo aumento. Hoy en d��a la respuesta a esa necesidad es la computaci��n en la nube, pero requiere que las aplicaciones sean no s��lo capaces de escalar, sino de hacerlo de forma el��stica [22]. Desgraciadamente no hay ninguna primitiva de sistema distribuido de slicing que soporte un particionamiento del estado interno [33] junto con un cambio en caliente, adem��s de que los sistemas cloud actuales como OpenStack u OpenNebula no ofrecen directamente una monitorizaci��n el��stica. Esto implica que hay un problema bilateral: c��mo puede una aplicaci��n escalar de forma el��stica y c��mo monitorizar esa aplicaci��n para saber cu��ndo escalarla horizontalmente. E-SilboPS es la versi��n el��stica de SilboPS y se adapta perfectamente como soluci��n para el problema de monitorizaci��n, gracias al paradigma publicador/subscriptor basado en contenido y, a diferencia de otras soluciones [5], permite escalar eficientemente, para cumplir con la carga de trabajo sin sobre-provisionar o sub-provisionar recursos. Adem��s est�� basado en un algoritmo recientemente dise��ado que muestra como a��adir elasticidad a una aplicaci��n con distintas restricciones sobre el estado: sin estado, estado aislado con coordinaci��n externa y estado compartido con coordinaci��n general. Su evaluaci��n ense��a como se pueden conseguir notables speedups, siendo el nivel de red el principal factor limitante: de hecho la eficiencia calculada (ver Figura 5.8) demuestra c��mo se comporta cada configuraci��n en comparaci��n con las adyacentes. Esto permite conocer la tendencia actual de todo el sistema, para saber si la siguiente configuraci��n compensar�� el coste que tiene con la ganancia que lleva en el throughput de notificaciones. Se tiene que prestar especial atenci��n en la evaluaci��n de los despliegues con igual coste, para ver cu��l es la mejor soluci��n en relaci��n a una carga de trabajo dada. Como ��ltimo an��lisis se ha estimado el overhead introducido por las distintas configuraciones a fin de identificar el principal factor limitante del throughput. Esto ayuda a determinar la parte secuencial y el overhead de base [26] en un despliegue ��ptimo en comparaci��n con uno sub��ptimo. Efectivamente, seg��n el tipo de carga de trabajo, la estimaci��n puede ser tan baja como el 10 % para un ��ptimo local o tan alta como el 60 %: esto ocurre cuando se despliega una configuraci��n sobredimensionada para la carga de trabajo. Esta estimaci��n de la m��trica de Karp-Flatt es importante para el sistema de gesti��n porque le permite conocer en que direcci��n (ampliar o reducir) es necesario cambiar el despliegue para mejorar sus prestaciones, en lugar que usar simplemente una pol��tica de ampliaci��n. ABSTRACT The application of pervasive computing is extending from field-specific to everyday use. The Internet of Things (IoT) is the shiniest example of its application and of its intrinsic complexity compared with classical application development. The main characteristic that differentiates pervasive from other forms of computing lies in the use of contextual information. Some classical applications do not use any contextual information whatsoever. Others, on the other hand, use only part of the contextual information, which is integrated in an ad hoc fashion using an application-specific implementation. This information is handled in a one-off manner because of the difficulty of sharing context across applications. As a matter of fact, the application type determines what the contextual information is. For instance, for an imaging editor, the image is the information and its meta-data, like the time of the shot or camera settings, are the context, whereas, for a file-system application, the image, including its camera settings, is the information and the meta-data external to the file, like the modification date or the last accessed timestamps, constitute the context. This means that contextual information is hard to share. A communication middleware that supports context decidedly eases application development in pervasive computing. However, the use of context should not be mandatory; otherwise, the communication middleware would be reduced to a context middleware and no longer be compatible with non-context-aware applications. SilboPS, our implementation of content-based publish/subscribe inspired by SIENA [11, 9], solves this problem by adding two new elements to the paradigm: the context and the context function. Context represents the actual contextual information specific to the message to be sent or that needs to be notified to the subscriber, whereas the context function is evaluated using the publisher���s context and the subscriber���s context to decide whether the current message and context are useful for the subscriber. In this manner, context logic management is decoupled from context management, increasing the flexibility of communication and usage across different applications. Since the default context is empty, context-aware and classical applications can use the same SilboPS, resolving the syntactic mismatch that there is between the two categories. In any case, the possible semantic mismatch is still present because it depends on how each application interprets the data, and it cannot be resolved by an agnostic third party. The IoT environment introduces not only context but scaling challenges too. The number of sensors, the volume of the data that they produce and the number of applications that could be interested in harvesting such data are growing all the time. Today���s response to the above need is cloud computing. However, cloud computing applications need to be able to scale elastically [22]. Unfortunately there is no slicing, as distributed system primitives that support internal state partitioning [33] and hot swapping and current cloud systems like OpenStack or OpenNebula do not provide elastic monitoring out of the box. This means there is a two-sided problem: 1) how to scale an application elastically and 2) how to monitor the application and know when it should scale in or out. E-SilboPS is the elastic version of SilboPS. I t is the solution for the monitoring problem thanks to its content-based publish/subscribe nature and, unlike other solutions [5], it scales efficiently so as to meet workload demand without overprovisioning or underprovisioning. Additionally, it is based on a newly designed algorithm that shows how to add elasticity in an application with different state constraints: stateless, isolated stateful with external coordination and shared stateful with general coordination. Its evaluation shows that it is able to achieve remarkable speedups where the network layer is the main limiting factor: the calculated efficiency (see Figure 5.8) shows how each configuration performs with respect to adjacent configurations. This provides insight into the actual trending of the whole system in order to predict if the next configuration would offset its cost against the resulting gain in notification throughput. Particular attention has been paid to the evaluation of same-cost deployments in order to find out which one is the best for the given workload demand. Finally, the overhead introduced by the different configurations has been estimated to identify the primary limiting factor for throughput. This helps to determine the intrinsic sequential part and base overhead [26] of an optimal versus a suboptimal deployment. Depending on the type of workload, this can be as low as 10% in a local optimum or as high as 60% when an overprovisioned configuration is deployed for a given workload demand. This Karp-Flatt metric estimation is important for system management because it indicates the direction (scale in or out) in which the deployment has to be changed in order to improve its performance instead of simply using a scale-out policy.

Abstract interpretation-based code certification for pervasive systems: Preliminary experiments

Proof carrying code is a general methodology for certifying that the execution of an untrusted mobile code is safe, according to a predefined safety policy. The basic idea is that the code supplier attaches a certif��cate (or proof) to the mobile code which, then, the consumer checks in order to ensure that the code is indeed safe. The potential benefit is that the consumer's task is reduced from the level of proving to the level of checking, a much simpler task. Recently, the abstract interpretation techniques developed in logic programming have been proposed as a basis for proof carrying code [1]. To this end, the certif��cate is generated from an abstract interpretation-based proof of safety. Intuitively, the verification condition is extracted from a set of assertions guaranteeing safety and the answer table generated during the analysis. Given this information, it is relatively simple and fast to verify that the code does meet this proof and so its execution is safe. This extended abstract reports on experiments which illustrate several issues involved in abstract interpretation-based code certification. First, we describe the implementation of our system in the context of CiaoPP: the preprocessor of the Ciao multi-paradigm (constraint) logic programming system. Then, by means of some experiments, we show how code certification is aided in the implementation of the framework. Finally, we discuss the application of our method within the ��rea of pervasive systems which may lack the necessary computing resources to verify safety on their own. We herein illustrate the relevance of the information inferred by existing cost analysis to control resource usage in this context. Moreover, since the (rather complex) analysis phase is replaced by a simpler, efficient checking process at the code consumer side, we believe that our abstract interpretation-based approach to proof-carrying code becomes practically applicable to this kind of systems.