Midgard: um middleware baseado em componentes e orientado a recursos para redes de sensores sem fio

摘要

On the last years, several middleware platforms for Wireless Sensor Networks(WSN) were proposed. Most of these platforms does not consider issues of howintegrate components from generic middleware architectures. Manyrequirements need to be considered in a middleware design for WSN and thedesign, in this case, it is possibility to modify the source code of the middlewarewithout changing the external behavior of the middleware. Thus, it is desiredthat there is a middleware generic architecture that is able to offer an optimalconfiguration according to the requirements of the application. The adoption ofmiddleware based in component model consists of a promising approachbecause it allows a better abstraction, low coupling, modularization andmanagement features built-in middleware. Another problem present in currentmiddleware consists of treatment of interoperability with external networks tosensor networks, such as Web. Most current middleware lacks the functionalityto access the data provided by the WSN via the World Wide Web in order totreat these data as Web resources, and they can be accessed throughprotocols already adopted the World Wide Web. Thus, this work presents theMidgard, a component-based middleware specifically designed for WSNs,which adopts the architectural patterns microkernel and REST. The microkernelarchitectural complements the component model, since microkernel can beunderstood as a component that encapsulates the core system and it isresponsible for initializing the core services only when needed, as well asremove them when are no more needed. Already REST defines a standardizedway of communication between different applications based on standardsadopted by the Web and enables him to treat WSN data as web resources,allowing them to be accessed through protocol already adopted in the WorldWide Web. The main goals of Midgard are: (i) to provide easy Web access todata generated by WSN, exposing such data as Web resources, following theprinciples of Web of Things paradigm and (ii) to provide WSN applicationdeveloper with capabilities to instantiate only specific services required by theapplication, thus generating a customized middleware and saving noderesources. The Midgard allows use the WSN as Web resources and still providea cohesive and weakly coupled software architecture, addressinginteroperability and customization. In addition, Midgard provides two servicesneeded for most WSN applications: (i) configuration and (ii) inspection andadaptation services. New services can be implemented by others and easilyincorporated into the middleware, because of its flexible and extensiblearchitecture. According to the assessment, the Midgard provides interoperabilitybetween the WSN and external networks, such as web, as well as betweendifferent applications within a single WSN. In addition, we assessed the memoryconsumption, the application image size, the size of messages exchanged inthe network, and response time, overhead and scalability on Midgard. Duringthe evaluation, the Midgard proved satisfies their goals and shown to bescalable without consuming resources prohibitively