Reliable distributed data stream management in mobile environments

The proliferation of sensor technology, especially in the context of embedded systems, has brought forward novel types of applications that make use of streams of continuously generated sensor data. Many applications like telemonitoring in healthcare or roadside traffic monitoring and control particularly require data streammanagement (DSM) to be applications are deployed in a failure-prone distributed setting including resourcelimited mobile devices, for instance in applications which aim at remotely monitoring mobile patients. In this paper, we introduce amodel for distributed and reliable DSM. The contribution of this paper is threefold. First, in analogy to the SQL isolation levels, we define levels of reliability and describe necessary consistency constraints for distributed DSM that specify the tolerated loss, delay, or re-ordering of data stream elements, respectively. Second, we use this model to design and analyze an algorithm for reliable distributed DSM, namely efficient coordinated operator checkpointing (ECOC). We show that ECOC provides lossless and delay-limited reliable data streammanagement and thus can be used in critical application domains such as healthcare, where the loss of data streamelements cannot be tolerated. Third, we present detailed performance evaluations of the ECOC algorithm running onmobile, resource-limited devices. In particular, we can show that ECOC provides a high level of reliability while, at the same time, featuring good performance characteristics with moderate resource consumption. & 2010 Elsevier B.V. All rights reserved.