The support for the expression data type in a relational database system allows storing of conditional expressions as data in database tables and evaluating them using SQL queries. In the context of this new capability, expressions can be interpreted as descriptions, queries, and filters, and this significantly broadens the use of a relational database system to support new types of applications. The paper presents an overview of the expression data type, relates expressions to descriptions, queries, and filters, considers applications pertaining to information distribution, demand analysis, and task assignment, and shows how these applications can be easily supported with improved functionality.