摘要 : In this paper, we present a set of parameters able to exactly model topologies of object references in object-oriented databases. These parameters are important since they are used to model query execution strategy costs for optim... 展开 In this paper, we present a set of parameters able to exactly model topologies of object references in object-oriented databases. These parameters are important since they are used to model query execution strategy costs for optimization. The model we present considers also the cases of multivalued attributes and null references. Moreover, a set of derived parameters are introduced and their mathematical derivations are shown. These derived parameters are important, since they allow selectivity of nested predicates to be estimated. Moreover, they are used in estimating storage, access, and update costs for a number of access structures specifically tailored to efficiently support object-oriented queries. 收起