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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jss.2010.08.018 Byline: Zijing Tan (a), Chengfei Liu (b), Wei Wang (a), Baile Shi (a) Keywords: XML; inconsistent; Query; Constraint Abstract: When data sources are virtually integrated, there is no common and centralized method to maintain global consistency, so inconsistencies with regard to global integrity constraints are very likely to occur. In this paper, we consider the problem of defining and computing consistent query answers when queries are posed to virtual XML data integration systems, which are specified following the local-as-view approach. We propose a powerful XML constraint model to define global constraints, which can express keys and functional dependencies, and which also extends the newly introduced conditional functional dependencies to XML. We provide an approach to defining XML views, which supports not only edge-path mappings but also data-value bindings to express the join operator. We give formal definitions of repair and consistent query answers with the XML data integration settings. Given a query on the global system, we present a two-step method to compute consistent query answers. First, the given query is transformed using the global constraints, such that to run the transformed query on the original global system will generate exactly the consistent query answers. Because the global instance is not materialized, the query on the global instance is then rewritten in the form of queries on the underlying data sources by reversing rules in view definitions. We illustrate that the XPath query transformations can be implemented in XQuery. Finally, we implement prototypes of our method and evaluate our algorithms in the experiments. Author Affiliation: (a) School of Computer Science, Fudan University, Shanghai, China (b) Faculty of Information and Communication Technologies, Swinburne University of Technology, Australia Article History: Received 11 December 2009; Revised 6 August 2010; Accepted 9 August 2010

In this article, we address the problem of how to extend the definition of functional dependencies (FDs) in incomplete relations to XML documents (called XFDs) using the well-known strong satisfaction approach.We propose a syntactic definition of strong XFD satisfaction in an XML document and then justify it by showing that, similar to the case in relational databases, for the case of simple paths, keys in XML are a special case of XFDs. We also propose a normal form for XML documents based on our definition of XFDs and provide a formal justification for it by proving that it is a necessary and sufficient condition for the elimination of redundancy in an XML document. Categories and Subject Descriptors: H.2.1 [Database Management]: Logical Design--Data models; normal forms; schema and subschema; H.2.3 [Database Management]: Languages--Data description languages (DDL) General Terms: Design, Management, Theory Additional Key Words and Phrases: XML, normalization, functional dependency

While keyword query empowers ordinary users to search vast amount of data, the ambiguity of keyword query makes it difficult to effectively answer keyword queries, especially for short and vague keyword queries. To address this challenging problem, in this paper we propose an approach that automatically diversifies XML keyword search based on its different contexts in the XML data. Given a short and vague keyword query and XML data to be searched, we first derive keyword search candidates of the query by a simple feature selection model. And then, we design an effective XML keyword search diversification model to measure the quality of each candidate. After that, two efficient algorithms are proposed to incrementally compute top-$k$ qualified query candidates as the diversified search intentions. Two selection criteria are targeted: the $k$ selected query candidates are most relevant to the given query while they have to cover maximal number of distinct results. At last, a comprehensive evaluation on real and synthetic data sets demonstrates the effectiveness of our proposed diversification model and the efficiency of our algorithms. [ABSTRACT FROM PUBLISHER]

We review the problem of finding contained rewritings (CRs) for XPath queries using XPath views. CR is proposed to cater for data integration scenarios, where views are unlikely to be complete due to the limited coverage of data sources, and hence equivalent rewritings are impossible to be found. As a result, we are usually required to find a maximal contained rewriting (MCR) for a query to provide the best possible answers. An MCR is a set of CRs, and may contain redundant CRs. Obviously, evaluating redundant CRs on materialized views is unnecessary. In this paper, we first address how to find the irredundant maximal contained rewriting (IMCR), i.e. all the irredundant CRs. We show that the existing approach ignores a type of situation, and turns out to be not sufficient. As a result, the only safe solution is a brute-force pairwise containment check for all the CRs. We then propose some heuristics to speed up the brute-force comparisons. When a materialized view is given, we propose how to evaluate the IMCR on the materialized view, which, to our knowledge, is the first work on optimizing the evaluation of a set of produced CRs on the materialized view by considering the inherent structural characteristics of the CRs. Our experiments show the effectiveness and efficiency of our algorithms. [ABSTRACT FROM AUTHOR]

Functional and inclusion dependency discovery is important to knowledge discovery, database semantics analysis, database design, and data quality assessment. Motivated by the importance of dependency discovery, this paper reviews the methods for functional dependency, conditional functional dependency, approximate functional dependency, and inclusion dependency discovery in relational databases and a method for discovering XML functional dependencies. [ABSTRACT FROM PUBLISHER]

Users are usually not familiar with the content and structure of the data when they explore the data source. However, to improve the exploration usability, they need some primary hints about the data source. These hints should represent the overall picture of the data source and include the trending issues that can be extracted from the query log. In this paper, we propose a two-phase interactive exploratory search framework for the clueless users that exploits the snippets for conducting the search on the XML data. In the first phase, we present the primary snippets that are generated from the keywords of the query log to start the exploration. To retrieve the primary snippets, we develop an A* search-based technique on the keyword space of the query log. To improve the performance of computations, we store the primary snippet computations in an index data structure to reuse it for the next steps. In the second phase, we exploit the co-occurring content of the snippets to generate more specific snippets with the user interaction. To expedite the performance, we design two pruning techniques called inter-snippet and intra-snippet pruning to stop unnecessary computations. Finally, we discuss a termination condition that checks the cardinality of the snippets to stop the interactive phase and present the final Top- l snippets to the user. Our experiments on real datasets verify the effectiveness and efficiency of the proposed framework. [ABSTRACT FROM AUTHOR]