The extended Datalog has more powerful expressiveness than SQL,and can describe more complicated semantics,such as looping and transition closure etc.

• (2 )针对该模型推广的 Datalog查询语言与结构化查询语言 SQL相比 ,具有更强的表达能力 ,可以描述诸如循环和传递闭包等复杂的应用语义。