Repositories of multimedia objects having multiple types of attributes e.g., image, text are becoming increasingly common. A selection on these attributes will typically produce not just a set of objects, as in the traditional relational query model ltering, but also a grade of match associated with each object, indicating how well the object matches the selection condition ranking. Also, multimedia repositories may allow access to the attributes of each object only through indexes. We investigate how to optimize the processing of queries over multimedia repositories. A key issue is the choice of the indexes used to search the repository. We de ne an execution space that is searchminimal, i.e., the set of indexes searched is minimal. Although the general problem of picking an optimal plan in the search-minimal execution space is NP-hard, we solve the problem e ciently when the predicates in the query are independent. We also show that the problem of optimizing queries that ask for a ...