Jana Neumann

Efficient XML usage within wireless sensor networks

Integrating wireless sensor networks in heterogeneous networks is a complex task. A reason is the absence of a standardized data exchange format that is supported in all participating sub networks. XML has evolved to the de facto standard data exchange format between heterogeneous networks and systems. However, XML usage within sensor networks has not been introduced because of the limited hardware resources. In this paper, we introduce XML template objects making XML usage applicable within sensor networks. This new XML data binding technique provides significant high compression results while still allowing dynamic XML processing and XML navigation. This is a step towards more complex but exchangeable data management in sensor networks and the extension of the service-oriented paradigm to sensor network application engineering.

Redundancy Infrastructure for Service-Oriented Wireless Sensor Networks

Transfering the paradigm of service-oriented architecture (SOA) to sensor networks became an important research area in the last years. Amongst others, a couple of approaches deal with the flexible and robust service discovery and usage of services which takes the unsteady nature of WSNs into account. However, the approaches do not consider the case that services may get unavailable during their activity phase because of node failures. In this case, already collected or computed data will get lost and the service request of the service consumer remains unanswered. In this paper, we propose a redundancy infrastructure for service-oriented WSNs which deals with this special problem. The framework consists of an adaptive data replication technique and a service recovery solution. Whereas the replication technique ensures the survival beyond node failures, the recovery protocol restarts a failed service using the replicated data and enables the service to continue its functionality.

Integrating standardized transaction protocols in service-oriented wireless sensor networks

Despite much research in the area of wireless sensor networks in recent years, the programming of sensor nodes is still time-consuming and tedious. A new paradigm which seems to be qualified to simplify the programming of sensor networks is the Service Oriented Architecture. The composition of simple services to more complex ones can be a convenient way to design applications. To enable the sophisticated techniques known from service oriented architectures like replication and migration of services, a transaction model for sensor networks is required. In this paper, we study the applicability of the standard commit protocols Two Phase Commit (2PC) and Transaction Commit On Timeout and show in experiments with real sensor nodes that 2PC can enable consistent service migration in wireless sensor networks.

Adaptive Quality-Aware Replication in Wireless Sensor Networks

Typical sensor network deployments are usually built for long-term usage. Additionally, the sensor nodes are often exposed to harsh environmental influences. Due to these constraints, it is mandatory for applications to be able to compensate the failure of nodes. Providing a persistent storage even in the presence of failing nodes demands for replication within the sensor network. However, recent work in the field of replication in sensor networks often does not consider the suitability of the sensor nodes to store replicas in terms of e.g. available storage, energy or connectivity. In this paper, we envision an adaptive quality-aware replication scheme which enables the storage of replicas based on a scoring system reflecting the suitability of a replica node. Furthermore, we propose an adaptable data migration strategy using a weighting function to achieve an adequate placement for the replicas. A resilient storage strategy enables the survival of replicas after migration despite unpredictable node failures. We expect that our replication scheme highly increases the availability of sensor network data despite of node failures and network partitioning requiring only a small number of replicas within the network.

DySSCo - A Protocol for Dynamic Self-Organizing Service Coverage

Service oriented middleware draws a lot of attention in current research on sensor networks. The automatic distribution of services within a network and the preservation of this distribution is a fundamental aspect of network applications with self-x properties. The network gains the ability to react on mobility, network fragmentation, node failures and new user demands. This paper proposes a distributed self-organizing algorithm for service distribution and preservation of this distribution using demanded coverages for the services. After discussing the theory of the convergence of the algorithm, this paper presents a real-world deployment of a sensor network scenario and evaluates the performance of the algorithm.

Analysis and Comparison of Atomic Commit Protocols for Adaptive Usage in Wireless Sensor Networks

Despite many research in the area of wireless sensor networks (WSNs) in recent years, the programming of sensor nodes is still time-consuming and tedious. One of the new paradigms which seem to be qualified to simplify the programming of sensor networks are service oriented architectures (SOAs). The composition of simple services to more complex ones can be a convenient way to design own applications. However, to enable the sophisticated techniques known from SOAs like replication and migration of services, a transactional model for WSNs is needed. In this paper, we compare the applicability of the standard commit protocol Two Phase Commit (2PC) and the Cross Layer Commit Protocol (CLCP) \cite{Obermeier2008a, Obermeier2008} to our scenario and present our own protocol Two Phase Commit with Caching (2PCwC). We show that the best results in terms of transmitted bytes per commit decision and memory consumption can be achieved if the appropriate protocol is chosen adaptively during runtime.

Stream-Based XML Template Compression for Wireless Sensor Network Data Management

Using structured data formats like XML in wireless sensor networks to support exchangeability and heterogeneity on application level has become an important research topic in the area of large scale networked sensing systems. Besides, the usage of XML encourages the adaptation of service oriented programming techniques to simplify sensor network application engineering. While the sensor nodes still have significant resource limitations in terms of energy and memory capacity and computational power, recent data management approaches show positive results to bridge this resource gap. Nevertheless, further optimizations are needed to enhance the application range to support larger sets of data within the networks. In this work we present an optimization for a template object compression scheme that is based on a stream-oriented XML compression and supports dynamic data management and query evaluation on the compressed data. We hereby present a complete solution for XML compression, data processing and query evaluation that can be further embedded in the engineering process to support developers. The presented solutions are evaluated and result into significant improvements in comparison to previous approaches, when processing complex large scale XML documents.

Efficient XML data and query integration in the wireless sensor network engineering process

Purpose – In the last decade, XML has become the de facto standard for data exchange in the world wide web (WWW). The positive benefits of data exchangeability to support system and software heterogeneity on application level and easy WWW integration make XML an ideal data format for many other application and network scenarios like wireless sensor networks (WSNs). Moreover, the usage of XML encourages using standardized techniques like SOAP to adapt the service‐oriented paradigm to sensor network engineering. Nevertheless, integrating XML usage in WSN data management is limited by the low hardware resources that require efficient XML data management strategies suitable to bridge the general resource gap. The purpose of this paper is to present two separate strategies on integrating XML data management in WSNs.Design/methodology/approach – The paper presents two separate strategies on integrating XML data management in WSNs that have been implemented and are running on todays sensor node platforms. The p...

A service-oriented operating system and an application development infrastructure for wireless sensor networks

Due to the highly distributed nature and special basic conditions such as limited resources, implementing and maintaining a sensor network application is a tedious task. In this demonstration we present a service-oriented operating system for sensor nodes and a framework that allows a composition of services on the nodes. We show how sensor network applications can be composed and modified by using different services.

SWOBE - embedding the semantic web languages RDF, SPARQL and SPARUL into java for guaranteeing type safety, for checking the satisfiability of queries and for the determination of query result types

The Semantic Web and its technologies become increasingly important. As more and more Semantic Web applications are being used, developing more stable Semantic Web applications becomes a key issue. The state-of-the-art in programming Semantic Web applications is using complex application programming interfaces of Semantic Web frameworks, where extensive tests are necessary for the detection of errors, although many types of errors could be detected already at compile time. In this paper, we propose an embedding of Semantic Web languages into the java programming language, such that Semantic Web data and queries can be transparently used, type safety is guaranteed, and already at compile time, syntax errors of Semantic Web data and queries are reported, unsatisfiable queries are detected and the types of query results are determined. A demonstration of our system is available online.