The success of the World Wide Web is boosting the development of multimedia database systems and their integration into the internet. For the documents stored and exchanged in the Web there is a variety of multimedia data formats differing in aspects such as resolution, sampling rate, and compression. Furthermore there is a large heterogeneity of Web browsers, the data formats they support, and their network access. Thus storage servers have to store and proxy servers have to transfer many different formats. However, the data formats are not independent from each other but interrelated by conversion tools. There is a large number of alternatives for storage and proxy servers to store some formats or to transfer them via the network and to compute the remaining ones by applying conversion tools. To determine an optimal choice is a nontrivial optimization problem and is subject to changes of the parameters such as query profile, available disk storage, and network bandwidth. We examine the outlined optimization problem in the context of object-oriented databases and illustrate our approach by a practical application