Chases and Bag-Set Certain Answers
  In this paper we show that the chase technique is powerful enough to capture the bag-set semantics of conjunctive queries over IDBs and IDs and TGDs. In addition, we argue that in such cases it provides efficient (LogSpace) query evaluation algorithms and that, moreover, it can serve as a basis for evaluating some restricted classes of aggregate queries under incomplete information. 
Camilo Thorne
cs.DB