1. A method for evaluating a conjunctive query, the method executed as a computer program by a general purpose computer, the conjunctive query comprising an at least one first predicate, the first predicate can be evaluated using a first engine, and an at least one second predicate, the at the least one second predicate can be evaluated using a second engine, the method comprising the steps of: a. activating the first engine to be executed by the computing platform to evaluate the at least one first predicate to obtain first temporary results; and b. activating the second engine be executed by the computing platform to use the first temporary results to evaluate the at least one second predicate so as to obtain second temporary results.