Educe is a logic programming system for handling large knowledge bases it was constructed by fully integrating the logic programming language prolog and the relational data base management system Ingres educe uses a hybrid strategy for the evaluation of queries this strategy is based on two contrasting strategies the strategy known as sets retrieval transforms recursive and non-recursive queries into a form suitable for evaluation by a relational data base management system. the other strategy known as one-tuple-at-a-time evaluates queries by imitating the evaluation strategy of the programming language prolog In earlier versions of educe users selected the strategy by using two different query languages in order to remove this responsibility from the user algorithms to map expressions from either of the languages into the other were implemented and added to educe this paper briefly reviews the implementation of both evaluators and the mappings compares the basic strategies of evaluation and then proceeds to explain Educes own strategy.