Introduction A statistical database typically contains information about n individuals where n is very large. A statistical database system gives users the ability to both obtain statistical information (like average, median, count) and preserve the privacy of any individual. Examples include census and medical databases.

-featured database systems and can answer only a small set of queries over their data (for example, forms on the WWW restrict the set of queries one can ask). (3) Since the number of sources is very large, effective techniques are needed to prune the set of information sources accessed to answer a query. (4

Ad hoc networks with high mobility profiles suffer from the problem of repeated route discoveries that need to be initiated frequently due to link breakages on active routes. Besides, all ad hoc networks are prone to high routing overhead due to query flooding during route discovery. Existing

strategies (sips) to restrict bottom-up evaluation to facts potentially relevant to the query. It is of interest to extend these transformations to all logic programs with negation, and identify classes of programs and sips for which these transformations preserve well-founded models with respect

This paper considers the problem of providing security to statistical databases against disclosure of confidential information. Security-control methods suggested in the literature are classified into four general approaches: conceptual, query restriction, data perturbation, and output perturbation

The problem of searching the elements of a set that are close to a given query element under some similarity criterion has a vast number of applications in many branches of computer science, from pattern recognition to textual and multimedia information retrieval. We are interested in the rather

Data perturbation and query restriction are two of the main methods that have been developed to protect confidential data in statistical database systems. In the former the confidential data is systematically changed to maintain its distributional properties, and to yield answers to queries

number restrictions. To the best of our knowledge, this yields the first decidability result on containment of conjunctive queries with regular expressions. Finally, we prove that the problem is undecidable for the case where we admit inequalities in q′.

it does, oc-casionally transmits a propositional clause2 to the CMS. The Reasoner is also permitted to query the CMS any time it feels so inclined. A query takes the form of a proposi-tional clause C. The CMS is expected to respond with every shortest clause S for which the clause S V C is a log

may impose some restrictions on the type and number of probes that they are willing to accept. We adapt our sequential query processing technique and introduce an efficient algorithm that maximizes sourceaccess parallelism to minimize query response time, while satisfying source-access constraints.