Sequences of queries to a database system can have structure. Recognizing this structure is a kind of parsing , analogous to the parsing of sentences. We present two rather different approaches to recognition for exploitation. The first is a rule-based system that examines superficial aspects of a query sequence to postulate preferences between sets mentioned in the queries. The second is a deeper, but more limited model based on decision theory, which assigns utilities and suitability probabilities to individual set items, and attempts to explain set preferences on that basis. Both of these methods have disadvantages, and their performance is difficult to analyze because of the fuzzy nature of the application, but it is hoped they can form the basis for more comprehensive man-machine interfaces.