A Novel Air Index Scheme for Twig Queries in On-Demand XML Data Broadcast

Data broadcast is an efficient way for information dissemination in wireless mobile environments, and on-demand XML data broadcast is one of the most important research issues in this area. Indexing XML data on wireless channel is critical for this issue since energy management is very important in wireless mobile environments. Previous works have focused on air index schemes for single path queries. In this paper, we propose a novel air index scheme that builds concise air indexes for twig queries in on-demand XML data broadcast. We adopt the Document Tree structure as the basic air index structure for twig queries and propose to prune redundant structures of the basic Document Tree indexes to reduce the energy consumption. Then we propose to combine all the pruned indexes into one which can eliminate structure redundancy among the indexes to further reduce the energy consumption. Our preliminary experiments show that our air index scheme is very effective and efficient, as it builds concise air indexes and supports twig queries without losing any precision.