Spatio-temporal Conceptual Schema Development for Wide-Area Sensor Networks
A Wide-Area Sensor Network (WASN) is a collection of heterogeneous sensor networks and data repositories spread over a wide geographic area. The diversity of sensor types and the regional differences over which WASNs operate result in semantic interoperab
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Oak Ridge National Laboratory PO Box 2008 MS 6017 Oak Ridge, TN 37831-6017 {shankarm,sorokina,bhaduribl,resseguiedr}@ornl.gov Department of Computer Science and Engineering, University of Minnesota 200 Union ST SE 4192S Minneapolis, MN 55414 {shekhar,jyoo}@cs.umn.edu
Abstract. A Wide-Area Sensor Network (WASN) is a collection of heterogeneous sensor networks and data repositories spread over a wide geographic area. The diversity of sensor types and the regional differences over which WASNs operate result in semantic interoperability mismatches among sensor data, and a difficulty in agreeing on methods for sensor data access and exchange. We assume that sensors and their associated data have an explicit spatio-temporal basis (or tagging) in their representation. In this paper, we describe a spatio-temporal looselycoupled federated database model for the WASN data storage problem that of unifying query and data representation given a heterogeneous WASN - and propose a conceptual schema to ease the problem of integration of sensor data representations. This is a continuing and critical challenge as sensor networks become more ubiquitous and data interoperation becomes increasing vital for a variety of applications (such as homeland security, transportation, environmental monitoring, etc.). We employ a top-down ontology-driven software development methodology. We use the SNAP/SPAN ontology as a sample framework for the conceptual schema. We compare our methodology of conceptual schema development with a bottom-up entity-oriented schema construction and discuss the differences in the two approaches. A unique contribution is the discussion of deployment experiences to evaluate proposed approaches in the context of a concrete WASN testbed.
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Introduction
We address the problem of unifying sensor data representation (e.g., for queries and storage) in Wide-Area Sensor Networks (WASNs). A WASN is a collection of heterogeneous sensor networks and data repositories spread over a wide geographic area (e.g., a deployment across one or more states). We aim to find commonality in the representation of the data records and their semantic description given the heterogeneity of the constituent components. We observe that a majority of WASN-related data is explicitly or implicitly spatio-temporally tagged. F. Fonseca, M.A. Rodr´ıguez, and S. Levashkin (Eds.): GeoS 2007, LNCS 4853, pp. 160–176, 2007. c Springer-Verlag Berlin Heidelberg 2007
Spatio-temporal Conceptual Schema Development for WASNs
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In many cases, it is easy to argue for an explicit spatial and temporal context for the WASN data, since the location and time-instant of data measurements directly affect the command and control operations within the WASN. Example domains for such sensor networks include transportation networks and CBRNE (Chemical-Biological-Radiation-Nuclear-Explosive, [1]) detection networks. Sensor networks have been a focus of much research in recent years [2,3]. Much of the research targets resource-constrained wireless sensor networks. WASNs,
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