A Query Language and User Interface for XML Information Retrieval

As XML is about to become the standard format for structured documents, there is an increasing need for appropriate information retrieval (IR) methods. Since classical IR methods were developed for unstructured documents only, the logical markup of XML documents poses new challenges. Since XML supports logical markup of texts both at the macro level (structuring markup for chapter, section, paragraph and so on) and the micro level (e.g., MathML for mathematical formulas, CML for chemical formulas), retrieval methods dealing with both kinds of markup should be developed. At the macro level, fulltext retrieval should allow for selection of appropriate parts of a document in response to a query, such as by returning a section or a paragraph instead of the complete document. At the micro level, specific similarity operators for different types of text or data should be provided (such as similarity of chemical structures, phonetic similarity for person names). Although a large number of query languages for XML have been proposed in recent years, none of them fully addresses the IR issues related to XML; especially, the core XQuery proposal of the W3C working group [4] offers no support for IR-oriented querying of XML sources; the discussion about extensions for text retrieval has started only recently (see the requirements document by Buxton and Rys [5] and the use cases by Amer-Yahia and Case [2]). There are only a few approaches that provide partial solutions to the IR problem, namely by taking into account the intrinsic imprecision and vagueness of IR; however, none of them are based on a consistent model of uncertainty (see section 5). In this paper, we present the query language XIRQL which combines the major concepts of XML querying with those from IR. XIRQL is based on