They are regarded not only as the important task in the fields of database system and machine learning by researchers, but also as the important field which can bring large reword by businessmen.

• 它不仅被许多研究人员看作是数据库系统和机器学习方面一个重要的研究课题，而且被许多工商界人士看作一个能带来巨大回报的重要领域。