An XML data allocation method on disks

XML recently has expanded its application areas: data formats in various information systems, communication protocols in distributed systems, and so on. Generally, XML data can be logically modeled as rooted tree. For the query processing of such data, path queries are widely used. In this paper, we present an optimal algorithm that places XML data on disks such that the number of disk accesses for path query processing is minimized. The proposed algorithm consists of two steps. First, we assign a number (called the mapping indicator) for each node of a tree in a bottom-up fashion, and in the next step we map the nodes to disk blocks using the assigned number. We analyze the optimality of the proposed method with some relevant proofs. We also show the proposed method provides good performance for various query types with XML data set. (c) 2006 Elsevier B.V. All rights reserved.