SQS - A Secure XML Querying System

Contemporary XML database querying systems have to deal with a rapidly growing amount of data and a large number of users. As a consequence, if access control is used to protect sensitive XML data at a fine-grained level, it is inefficient when it comes to query evaluation, since it is difficult to enforce access control on each node in an XML document when the user’s view needs to be computed. We design and develop a secure XML querying system namely SQS, where caching is used to store query results and security information. Depending on whether there is a cache hit or not, user queries are rewritten into secure system queries that are executed either on the cached query results or on the original XML document. When the cache is full, the entries may be replaced with various replacement schemes. We also experimentally demonstrate the performance of the SQS system.