Publications (1)0 Total impact
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ABSTRACT: Consider a network in which a collection of source nodes maintain and periodically update data objects for a collec-tion of sink nodes, each of which periodically accesses the data originating from some specified subset of the source nodes. We consider the task of efficiently relaying the dy-namically changing data objects to the sinks from their sources of interest. Our focus is on the following "push-pull" approach for this data dissemination problem. Whenever a data object is updated, its source relays the update to a designated subset of nodes, its push set; similarly, whenever a sink requires an update, it propagates its query to a des-ignated subset of nodes, its pull set. The push and pull sets need to be chosen such that every pull set of a sink inter-sects the push sets of all its sources of interest. We study the problem of choosing push sets and pull sets to minimize total global communication while satisfying all communica-tion requirements. We formulate and study several variants of the above data dissemination problem, that take into account differ-ent paradigms for routing between sources (resp., sinks) and their push sets (resp., pull sets) – multicast, unicast, and controlled broadcast – as well as the aggregability of the data objects. Under the multicast model, we present an op-timal polynomial time algorithm for tree networks, which yields a randomized O(log n)-approximation algorithm for n-node general networks, for which the problem is hard to approximate within a constant factor. Under the unicast * Chakinala, Kumarasubramanian,-59593-452-9/06/0007 . model, we present a randomized O(log n)-approximation al-gorithm for non-metric costs and a matching hardness re-sult. For metric costs, we present an O(1)-approximation and matching hardness result for the case where the inter-ests of any two sinks are either disjoint or identical. Finally, under the controlled broadcast model, we present optimal polynomial-time algorithms. While our optimization problems have been formulated in the context of data communication in networks, our prob-lems also have applications to network design and multicom-modity facility location and are of independent interest.