GUEST EDITORS' FOREWORD
Rewriting of Regular Expressions and Regular Path Queries
Inherent Complexity of Recursive Queries
Maximizing Sharing of Protected Information
A Framework for Measuring Differences in Data Characteristics
Hypertree Decompositions and Tractable Queries
Aggregate Operators in Constraint Query Languages
Querying Incomplete Information in Semistructured Data
Polymorphic Type Inference for the Relational Algebra
Tracking Join and Self-Join Sizes in Limited Storage
Papers to Appear in Forthcoming Issues