An interrelational grouping abstraction for heterogeneous sensors

In wireless sensor network applications, the potential to use cooperation to resolve user queries remains largely untapped. Efficiently answering a user's questions requires identifying the correct set of nodes that can answer the question and enabling coordination between them. In this article, we propose a query domain abstraction that allows an application to dynamically specify the nodes best suited to answering a particular query. Selecting the ideal set of heterogeneous sensors entails answering two fundamental questions— how are the selected sensors related to one another, and where should the resulting sensor coalition be located. We introduce two abstractions, the proximity function and the reference function , to precisely specify each of these concerns within a query. All nodes in the query domain must satisfy any provided proximity function, a user-defined function that constrains the relative relationship among the group of nodes (e.g., based on a property of the network or physical environment or on logical properties of the nodes). The selected set of nodes must also satisfy any provided reference function, a mechanism to scope the location of the query domain to a specified area of interest (e.g., within a certain distance from a specified reference point). In this article, we model these abstractions and present a set of protocols that accomplish this task with varying degrees of correctness. We evaluate their performance through simulation and highlight the tradeoffs between protocol overhead and correctness.