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In sensor networks, it is crucial to design and employ energy-efficient communication protocols, since nodes are battery-powered and thus their lifetimes are limited. This paper studies data dissemination in two-tiered networks comprised of stationary sensor nodes and mobile data users who request periodic sensor data updates. We propose a protocol called(More)
—Event detection plays an important role in wireless sensor network (WSN) applications such as battlefield surveillance and habitat monitoring. However, effective approaches for specifying events in a sensor network remain a challenge. In this paper we present MEDAL, a formal event description language. MEDAL is a modified Petri net which provides a more(More)
ÐDatabase systems for real-time applications must satisfy timing constraints associated with transactions in addition to maintaining data consistency. In addition to real-time requirements, security is usually required in many applications. Multilevel security requirements introduce a new dimension to transaction processing in real-time database systems. In(More)
— This paper describes the design of RESTORE, which is a framework for providing in-network event correlation and storage service for sensor environments. RESTORE uses a data-centric approach in which it partitions a sensor network into zones and maps every event to a zone. The sensor nodes in a zone make use of their cooperative storage resources and(More)
Despite the significant body of results in real-time scheduling, many real world problems are not easily supported. While algorithms such as Earliest Deadline First, Rate Monotonic, and the Spring scheduling algorithm can support sophisticated task set characteristics (such as deadlines, precedence constraints, shared resources, jitter, etc.), they are all(More)
Many real-time applications need data services in distributed environments. However, providing such data services is a challenging task due to long remote data accessing delays and stringent time requirements of real-time transactions. Replication can help distributed real-time database systems meet the stringent time requirements of application(More)