XML stream processing has recently become popular for many applications such as selective dissemination of information. Several approaches have been proposed and most of them are based on the idea of finite automata. Different from these approaches, this paper presents a novel and efficient method for evaluating XPath with predicates on XML streaming data. For linear XPath expressions, our appr...

We demonstrate the XISS/R system, an implementation of the XML Indexing and Storage System (XISS) on top of a relational database. The system is based on the XISS extended preorder numbering scheme, which captures the nesting structure of XML data and provides the opportunity for storage and query processing independent of the particular structure of the data. The system includes a web-based us...

In this paper, we propose a typology of the semantic transformations for XPath queries. We focus on two main areas. The first is structural transformation for XPath query, which can be semantically contracted, expanded or complemented using structural constraints. The second is semantic qualifier transformation where the predicates, specified by [ ], in an XPath query can be eliminated or trans...

Algorithms for answering XPath queries on Xml streams have been studied intensively in the last decade. Nevertheless, there still exists no solution with high efficiency and large coverage. In this paper, we introduce early nested word automata in order to approximate earliest query answering algorithms for nested word automata in a highly efficient manner. We show that this approximation can b...

We study the concept of earliest query answering as neededfor streaming XML processing with optimal memory man-agement. We derive lower complexity bounds showing thatearliest query answering for Forward XPath is not feasible inpolynomial time combined complexity except if P=NP. Wethen distinguish a fragment of Forward XPath with negationthat enjoys P-time earliest query ...

LOPiX is an implementation of XPathLog [May01b], an XML/XPath-native, rule-based programming language for manipulation and integration of XML documents. The main syntactical constructs are XPath expressions, extended with variables. Due to the close relationship with XPath, the semantics of rules is easy to grasp. In contrast to other approaches, the XPath syntax and semantics is also used for ...

XML Path Language (XPath) is the most important standard for navigation within XML documents nowadays. In this paper we present the state of our current research that is focused on using a functional framework based on simply typed lambda calculi and a general type system XML-λ for description of semantics of a query language. With such formalism we are able to describe the semantics of all lan...

The satisfiability test checks, whether or not the evaluation of a query returns the empty set for any input document, and can be used in query optimization for avoiding the submission and the computation of unsatisfiable queries. Thus, applying the satisfiability test before executing a query can save processing time and query costs. We focus on the satisfiability problem for queries formulate...

Recent studies have proposed structural summary techniques for path query evaluation on semi-structured data sources. One major line of this research has been the introduction of the DataGuide, 1-index, 2-index, and A(k) indices, and subsequent investigations and generalizations. Another recent study has considered structural characterizations of fragments of XPath, the standard path navigation...

This paper presents a novel and complementary technique to optimize an XPath query by minimizing its wildcard steps. Our approach is based on using a general composite axis called the layer axis, to rewrite a sequence of XPath steps (all of which are wildcard steps except for possibly the last) into a single layer-axis step. We describe an efficient implementation of the layer axis and present ...