1. A method performed by at least one computer processor, the method comprising: (1) storing data representing a plurality of classes and a plurality of instances in a bijective-set memory; (2) storing data representing class membership relationships between the plurality of classes and the plurality of instances in the bijective-set memory; (3) receiving data representing a query, wherein the query does not specify any table; (4) identifying an operation specified by the query; (5) identifying an operand specified by the query; (6) executing the query, comprising: (6)(a) identifying a table to be searched, based on the query; and (6)(b) performing the operation on the operand, including searching the identified table, to produce an output.