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...esigned to deal with recursion. Recently, a whole host of efficient storage structures and indexing schemes that summarize an XML document so that these problems can be dealt with have been developed =-=[14, 6, 9]-=-. Almost exclusively, these techniques put their focus on providing efficient support for sequences of / and//location steps, the regular path expressions, however. This is hardly adequate support for...

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...aditional (induced) subtrees, while we mine embedded subtrees. With the advent of XML as a data representation and exchange standard, there has been active work in indexing and querying XML documents =-=[15, 23, 2, 11]-=-, which are mainly tree (or graph) structured. To efficiently answer ancestordescendant queries various node numbering schemes similar to ours have been proposed [15, 23, 1]. Other work has looked at ...

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...thms. Similar to [14], [18] returns the set of MLCAs with explanations on why each node is an MLCA. A popular numbering scheme is to use a pair of numbers consisting of preorder and postorder numbers =-=[2, 17]-=-. Given two nodes and their pairs of numbers, it can be determined whether one of them is an ancestor of the other in constant time. However, this type of scheme is inefficient in finding the LCA of t...

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... of John. Since paths are represented as strings, existing algorithms and tools such as AGrep for string searching are applicable to processing these queries (see [10, 11, 12, 41] for a review). XISS =-=[64]-=- is a XML indexing and querying system designed to support regular path expressions. In each XML tree, each node is associated with a pair of integers enabling the determination of ancestor-descendant...

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.... pre(v2). Any node surrogate that satisfies these requirements may serve as a node representation equally well, and the database community has devised a variety of alternative ways to implement them =-=[25, 30]-=-. In XQuery, sequences host items of arbitrary type. The sequence (2,&quot;x&quot;,<a/>) leads to the depicted relational encoding (where γa denotes the surrogate of the XML node constructed by the node constru...

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...relational storage. Rather, our goal is to examine the effect of a covering index in each case. 6. RELATED WORK Tilere has been a considerable amount of' work on indexing for semi-structnred/XML data =-=[4, 6, 7, 9, 11, 12, 17]-=-. Almost all of this work has concentrated on indexing simplc path cxprcssions. In [16], thc authors propose a storage/indexing strategy in which data nodes are partitioned into relational tables by t...

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...pporting structural queries. 1. INTRODUCTION With the growing importance of XML in data exchange, much research has been done in providing flexible query mechanisms to extract data from XML documents =-=[11, 18, 16, 9, 6, 14]-=-. The semi-structured nature of XML data and the requirements on query flexibility pose unique challenges to database indexing methods. In this paper, we introduce a novel index structure, ViST 1 , wh...

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...which may then be serialized by a post-processing step [11]. We assume a minimalistic encoding of both, trees and ordered sequences of atomic values and nodes. Several existing XML mapping techniques =-=[3, 15] p-=-rovide these assumptions, and our compiler can easily be modified to target any such scheme. We exercise special care in translating the XQuery FLWOR construct. There is some tension between XQuery’...

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...ation as required by the XPath specification. 3. While previous contributions have indicated the superiority of path join algorithms over conventional tree traversals for a limited set of expressions =-=[10, 15, 16]-=-, we extend the application of path joins to implement large parts of the XPath query language and add support for keyword search on element and attribute content. The paper is organized as follows: T...