Date Added: Aug 2009
In this paper, the authors investigate the problem of view selection for workloads of conjunctive queries under bag semantics. In particular they aim to limit the search space of candidate viewsets. In that respect they start delineating the boundary between query workloads for which certain restricted search spaces suffice. They suffice in the sense that they do not compromise optimality in that they contain at least one of the optimal solutions. They start with the general case, where they give a tight condition that candidate views can satisfy and still the search space (thus limited) does contain at least one optimal solution.