Efficient Query Processing for XML Data Base

As the number of XML documents increases, the importance of building and querying native XML repositories becomes evident. An interesting and challenging aspect of such repositories is that part of the query evaluation process is the discovery of relevant data in addition to its retrieval. This discovery operation often requires a form of simple pattern matching: that is, it requires operations like "find all elements x containing a string s", or "find all elements x that have an element y as an ancestor." To solve this problem, the database community utilizes inverted list filtering, since the problem is so similar to that addressed in structured information retrieval applications. In addition to inverted list filtering, XML query processing naturally includes navigational access to XML data.