Wouter Horré

LooCI: a loosely-coupled component infrastructure for networked embedded systems

Considerable research has been performed in applying run-time reconfigurable component models to the domain of wireless sensor networks. The ability to dynamically deploy and reconfigure software components has clear advantages in sensor network deployments, which are typically large in scale and expected to operate for long periods in the face of node mobility, dynamic environmental conditions and changing application requirements. To date, research on component and binding models for sensor networks has primarily focused on the development of specialized component models that are optimized for use in resource-constrained environments. However, current approaches impose significant overhead upon developers and tend to use inflexible binding models based on remote procedure calls. To address these concerns, we introduce a novel component and binding model for networked embedded systems (LooCI). LooCI components are designed to impose minimal additional overhead on developers. Furthermore, LooCI components use a novel event-based binding model that allows developers to model rich component interactions, while providing support for easy interception, re-wiring and re-use. A prototype implementation of our component and binding model has been realised for the SunSPOT platform. Our preliminary evaluation shows that LooCI has an acceptable memory footprint and imposes minimal overhead on developers.

LooCI: The Loosely-coupled Component Infrastructure

Creating and managing applications for Wireless Sensor Networks (WSNs) is complicated by large scale, resource constraints and network dynamics. Reconfigurable component models minimize these complexities throughout the application lifecycle. However, contemporary component based middleware for WSNs is limited by its poor support for distribution. This paper introduces the Loosely-coupled Component Infrastructure (LooCI), a middleware for building distributed component-based WSN applications. LooCI advances the state-of-the-art by cleanly separating distributed concerns from component implementation, supporting application-level interoperability between heterogeneous WSN platforms and providing compatibility testing of bindings at runtime. Together, these features promote the safe and efficient composition and reconfiguration of distributed WSN applications. We evaluate the performance of LooCI on three classes of sensor nodes and demonstrate that these features can be provided with minimal overhead in terms of computation, memory and message passing.

A middleware platform to support river monitoring using wireless sensor networks

Flooding is a critical global problem, which is growing more severe due to the effects of climate change. This problem is particularly acute in the state of São Paulo, Brazil, where flooding during the rainy season incurs significant financial and human costs. Another critical problem associated with flooding is the high level of pollution present in urban rivers. Efforts to address these problems focus upon three key research areas: river monitoring, modelling of river conditions and incident response. This paper introduces a rich next-generation middleware platform designed to support wireless sensor network based environmental monitoring along with a supporting hardware platform. This system has been deployed and evaluated in a real-world river monitoring scenario in the city of São Carlos, Brazil.

DAVIM: Adaptable Middleware for Sensor Networks

Middleware services facilitate sensor-network application development. DAVIM is adaptable middleware that enables dynamic management of services and isolation between simultaneously running applications.

Building Wireless Sensor Network Applications with LooCI

Considerable research has been performed in applying run-time reconfigurable component models to the domain of wireless sensor networks. The ability to dynamically deploy and reconfigure software components has clear advantages in sensor networks, which are typically large in scale and expected to operate for long periods in the face of node mobility, dynamic environmental conditions, and changing application requirements. LooCI is a component and binding model that is optimized for use in resource-constrained environments such as Wireless Sensor Networks. LooCI components use a novel event-based binding model that allows developers to model rich component interactions, while providing support for run-time reconfiguration, reflection, and policy-based management. This paper reports on the design of LooCI and describes a prototype implementation for the Sun SPOT. This platform is then evaluated in context of a real-world river monitoring and warning scenario in the city of Sao Carlos, Brazil.

Applying a Multi-paradigm Approach to Implementing Wireless Sensor Network Based River Monitoring

This paper describes the application of the DisSeNT middleware to implement Wireless Sensor Network based river monitoring. DisSeNT provides LooCI, an efficient run-time reconfigurable component model, PMA, a lightweight policy-based management framework and QARI, a declarative quality-aware deployment framework. Using a river monitoring case-study, this paper analyses how these distinct software development paradigms can be used in a complimentary fashion to develop efficient wireless sensor network applications. The resulting system has been deployed and evaluated in a real-world river monitoring scenario in the city of São Carlos, Brazil.

On the integration of sensor networks and general purpose IT infrastructure

Integrating sensor networks with general purpose IT infrastructure has been confirmed as a complex problem in the development and management of industrial sensor applications. This integration is complex because a single general purpose application queries multiple sensor networks and a single sensor network has to serve multiple applications. This paper identifies three challenges that need to be addressed by middleware in order to enable this integration: federated management, interoperability and adaptability across the whole infrastructure. The paper presents a taxonomy of middleware solutions and positions the identified challenges in a survey of state-of-the-art middleware research we conducted earlier. By looking at sensor network middleware from an application (business) perspective, we come to the conclusion that time may have come to consolidate middleware efforts presented during the past years.

Supporting reconfiguration and re-use through self-describing component interfaces

Run-time reconfigurable component models have been highlighted as having particular potential in networked embedded systems. In these models, explicit interface definitions promote the re-use of generic units of functionality between application compositions, while run-time reconfiguration provides a mechanism to manage the dynamism of sensor network environments. Despite these advantages, in current systems, reliably re-using and reconfiguring distributed components is a complex undertaking. It requires a detailed understanding of the services offered by each component. The lack hereof effectively precludes run-time discovery and use of third-party components. This paper proposes the embedding of compact semantic descriptions in component interfaces and associated messages. These descriptions allow for efficient compatibility checking and therefore facilitate the run-time discovery and use of third-party component services. We demonstrate that this scheme is feasible in even the most resource-constrained sensor network environments.

Eliminating implicit dependencies in component models

A software component is defined as a unit of composition with contractually specified interfaces and explicit dependencies that may be independently deployed. Components form generic, re-usable software building blocks, which can be composed into applications and deployed by third parties. A good component model therefore must seek to minimize implicit dependencies in order to maximize re-use and composability. The benefits of component models have led to their widespread application in the area of networked embedded systems and particularly Wireless Sensor Networks. This paper first classifies and analyses the types of dependency that a component may be subject to. Next, we assess the success of contemporary component models in eliminating implicit dependencies and promoting re-usability. We then describe our efforts to reduce implicit distributed dependencies in the design of LooCI: the Loosely-coupled Component Infrastructure. We conclude with a call-to-arms for the component-based software engineering community that suggests avenues for future work.

QARI: Quality Aware Software Deployment for Wireless Sensor Networks

If we are to deploy sensor applications in a realistic business context, we must provide innovative middleware services to control and enforce required system behavior; in order to correctly interpret collected temperature data, for example, sensor applications require guarantees about minimal coverage and the number of available sensors. The extreme dynamism, scale and unreliability of wireless sensor networks represent major challenges in contemporary software management. This paper presents QARI, a middleware service for decentralized and quality aware software deployment, which offers a simple yet flexible way to define, enforce, and maintain software deployment specifications. We have evaluated QARI on the LooCI component model and the SunSPOT platform; results confirm that QARI enables quality aware software deployment for a single as well as multiple applications, and even in the presence of node failure and mobility.