Visual exploration and retrieval of XML document collections with the generic system X2

Abstract

Abstract. This article reports on the XML retrieval system X 2 which has been developed at the University of Munich over the last five years. In a typical session with X 2 , 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 combining structure and textual references are composed semiautomatically. After query evaluation, the full set of answers is presented in a visual and structured way. X 2 largely exploits the structure found in documents, queries and answers to enable new interactive visualization and exploration techniques that support mixed IR and database-oriented querying, thus bridging the gap between these three views on the data to be retrieved. Another salient characteristic of X 2 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 dynamically reordering and grouping retrieved elements once the complete answer set has been computed.

Exploiting native XML indexing techniques for XML retrieval in relational database systems

“…The element table has a cluster index on the pid , key, eid fields and a secondary index on the key, eid fields. Our native XML system is X 2 [24] (Sect. 5.2), combined with the CADG and BIRD.…”

“…A first set of experiments (Table 3) measures the performance gain of the RCADG (RC) over native XML retrieval with X 2 [24]. To avoid a handicap for the X 2 system which always matches the entire query graph, all query nodes are treated as result nodes here.…”

“…Query languages like XPath and XQuery are de-facto standards, and today applications relying on XML storage and retrieval scale up to the multi-gigabyte level. Motivated by the widespread use of XML, the development of native XML databases has received much attention [23,21,20,24]. Throughout this work, the term "native" subsumes systems whose evaluation kernel operates outside a general-purpose database system, Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page.…”

A Survey on Visual Query Systems in the Web Era

“…In paper [23] the XML structure is visualized as a GUI tree on the left part of the SchemaBrowser. There, nodes can be activated and can serve as a basis for automatically generating a query tree.…”

“…In X2 [23], the user selects nodes of interest in the XML diagram and the system automatically generates query trees from the nodes selected. An example can be seen in Figure 10 where the query 'I would like to see interesting recent papers on XML written by Sally Sonntag' is shown.…”