An Algebraic Approach to Recursive Inference
Recursion in the database context has traditionally been studied under the formalism of 1-st order logic. In particular, the bulk of the research effort in the last few years has been devoted to recursive Horn clauses. The authors reformulate the recursion problem in operator form. The relational operators are embedded in a partially ordered semiring with identity. This algebraic structure so obtained enables them to get more information about the mechanics of recursion. One of this is that they have been able to obtain a significant decomposition theorem for recursive queries.