Abstract: A stack-language interface between a client application and its underlying database. To query the database, the client application passes a search expression to a database API. The search expression includes simple operands, which define values for individual search criteria, and one or more operators, which define the logical relationship between two or more operands. Upon receiving the search expression, the database API searches the database to retrieve records satisfying the search criteria. For each record, the database API executes the search expression on the stack machine to determine if the record matches the search criteria as defined by the operands and operators in the search expression. Once the relevant records are retrieved, the database API may present a list of objects representing those records to the client application.