Visual Exploration and Retrieval of XML Document Collections with the Generic System X

An increasing number of documents found in digital libraries and on the Web are marked up with XML. Special information retrieval techniques for XML documents obviously help to improve precision and recall. At the same time, the structure found in documents, queries and answers allows for new interactive visualization and exploration techniques that bridge the gap between documents, queries and answers, present full answer sets in a flexible way and help users to satisfy their real information need. This article reports on the XML retrieval system X which has been developed at the University of Munich over the last five years. In a typical session with X, the user first browses a structural summary of the XML database in order to select interesting elements and keywords occurring in documents. Using this intermediate result, queries that combine structure and textual references are composed automatically. After query evaluation, the full set of answers is presented in a visual and structured way. A salient characteristic of X which distinguishes it from other visual query systems for XML is that it supports various degrees of detailedness in the presentation of answers, as well as techniques for re-ordering and grouping elements in the complete answer set.