A Novel Approach to Context-Aware Content-Based Middleware

Abstract

Realizado el acto de defensa y lectura de la Tesis el día de de 2016 en la E.T.S.I. Informáticos EL PRESIDENTE LOS VOCALESLA SECRETARIA AcknowledgementsI would like to express my gratitude to all those people who directly, indirectly or unconsciously have pushed me to improve myself continuously. AbstractThe 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. IIISince 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 coul...

A Technology-Agnostic Approach to Auto-Scale Services in Heterogeneous Clouds

“…As already mentioned, E-SilboPS is a context-aware content-based publish/subscribe middleware specially designed to be elastic. This middleware is the elastic version of SilboPS and was born as a result of a doctoral thesis [51] of which this work is its natural continuation. In addition, it has acquired great relevance as shown by its integration with technological paradigms that demand high performance and are transforming our lives such as Internet of Things (IoT), Smart Cities, Fog Computing [52,53,44], and more generally, in any event-driven architecture [54].…”

“…Figure 2.5 summarizes the message exchange during the scale-out operation of the Matcher layer. All information regarding the scale-out and scale-in algorithms of each of the operator layers can be found in [43,51,53]. As shown in Figure 2.5 by dashed lines, some coordination between the different layers is necessary to maintain consistency of system state.…”