SUMMARYIn service in the ubiquitous networking environment, it is expected that flexible interaction between the user and the things (resource) in the real world will become important. In order to realize such an interaction, there must be a system in which the resource to be utilized can be searched for with its attribute information as keys. Consequently, this paper proposes a DHT (distributed hash table)-based P2P search system using a new indexing method called pseudocandidate key indexing. A problem of the conventional DHT-based P2P search system is that a large amount of communication is needed in the search process. The proposed system attempts to deal with the problem by preparing an index for all search conditions which are useful to the user, thus reducing the amount of communication in the search. A simulation verifies that the proposed system is scalable.

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A sensor network covering a large area enables connection to various types of sensors and actuators, but application development becomes complicated because of the uncontrollable behavior of such a large number of devices. We propose the uTupleSpace model for uniform and indirect communication with two extensions to the original tuple space model. The extensions enable efficient range search for multidimensional keys and bi-directional communications. Our implementation of our proposed model also integrates load balancing by using a distributed hash table, and the experimental results indicate good scalability in multiple servers. The trial application of gathering and plotting GPS sensor data works well in the field.

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