A review on XML keyword query processing

Keyword search is gaining popularity for querying XML data now days as it relieves user from understanding the complex schemas of XML document and query languages such as XQuery and XPath. Various query processing techniques and efficient algorithms have been proposed in recent days to address the keyword search over XML data. The most popular techniques for XML keyword search today use query semantics ELCA (Exclusive LCA) and SLCA (Smallest LCA), both based on LCA (Lowest Common Ancestor). Among these ELCA captures more meaningful results compared with LCA and ELCA. However these techniques can result in redundant computation due to problems like common-ancestor-repetition (CAR) and visiting-useless-node (VUN). Irregular schemas of given XML document and missing elements in it are also problems of consideration in keyword query processing over XML data. In this paper we try to make an attempt to review various XML keyword query processing techniques. We also highlight some of the important issues associated with respective techniques and improvements done in order to address the issues and thereby improving overall efficiency of the XML keyword search query processing.