Purpose – eXtensible Markup Language (XML) data are data which are not necessarily constrained by a schema, XML is fast emerging as a standard for data representation and exchange on the world wide web, the ability to intelligently query XML data becomes increasingly important. Some XML graphical query languages for XML data have been proposed but they are either too complex or too limited in the power of expression and in their use. The purpose of this paper is to propose a recursive graphical query language for querying and restructuring XML data (RGQLX). The expressive power of RGQLX is comparable to Fixpoint. RGQLX language is a multi‐sorted graphical language integrating grouping, aggregate functions, nested queries and recursion. Design/methodology/approach – The methodology emphasizes on RGQLX's development which is base of G‐XML data model syntax to express a wide variety of XML queries, ranging from simple selection, to expressive data transformations involving grouping, aggregation and sorting. RGQLX allows users to express recursive visual queries in an elegant manner. RGQLX has an operational semantics based on the annotated XML, which serves to express queries and data trees in form of XML. The paper presents an algorithm to achieve the matching between data and query trees after translating a query tree into annotated XML. Findings – Developed and demonstrated were: a G‐XML model; recursive queries; annotated XML for the semantic operations and a matching algorithm. Research limitations/implications – The future research work on RGQLX language will be expanding it to include recursive aggregations. Practical implications – The algorithms/approaches proposed can be easily integrated in any commercial product to enhance the performance of XML query languages. Originality/value – The proposed work integrates various novel techniques for XML query syntax/semantic into a single language with a suitable matching algorithm. The power of this proposal is in the class of Fixpoint queries.
International Journal of Web Information Systems – Emerald Publishing
Published: Aug 30, 2011
Keywords: G‐XML; Nested queries; Aggregation; Aggregate functions; Recursive graphical queries; Fixpoint; Annotated XML and matching; Extensible markup language; Internet; Data modelling
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