CASE-DB is a real-time, single-user, relational prototype DBMS that permits the specification of strict time constraints for relational algebra queries. Given a time constrained nonaggregate relational algebra query and a "fragment chain" for each relation involved in the query, CASE-DB initially obtains a response to a modified version of the query and then uses an "iterative query evaluation" technique to successively improve and evaluate the modified version of the query, CASE-DB controls the risk of overspending the time quota at each step using a "risk control technique".

The problem of time-constrained query evaluation in a single-user database management system (DBMS) is considered. CASE-DB is a real-time, single user, relational prototype DBMS that uses the relational algebra as its query language. Given a nonaggregate query and a fragment chain for each input relation of the query. CASE-DB uses iterative query evaluation techniques to obtain a response first to a modified version of the query, and then to successively improved versions of the query. CASE-DB controls the risk of overspending the time quota at each step using a risk control technique. For periodically occurring queries, CASE-DB uses incremental query evaluation techniques that make sure that each operator in the query has at least one operand relation which contains the changes in the last period, and is expected to be very small compared to the actual database relation.>