Query Translation from XPath to SQL in the Presence of Recursive DTDs

摘要

The invention provides a system and method for translating XPATH queries into SQL queries with a simple least fixpoint (LFP) operator, which is already supported by most commercial RDBMS. The method comprises the steps of (a) rewriting an input query into a regular query, which is capable of capturing both DTD recursion and XPATH queries in a uniform framework; and (b) translating the regular query to an SQL query with LFP. The invention further provides optimization techniques for reducing the use of the LFP operator. As a result, the invention is capable of answering a large class of XPATH queries by means of only low-end RDBMS features already available in most RDBMS.