Johns Hopkins Medical InstitutionsRecent research on programming models for developing applications in the Grid has proposed component-based models as a viable approach, in which an application is composed of multiple interacting computational objects. We have been developing a framework, called filter-stream programming, for building data-intensive applications that query, analyze and manipulate very large data sets in a distributed environment. In this model, the processing structure of an application is represented as a set of processing units, referred to as filters. In this paper, we develop the problem of scheduling instances of a filter group. A filter group is a set of filters collectively performing a computation for an application. In particular, we seek the answer to the following question: should a new instance be created, or an existing one reused? We experimentally investigate the effects of instantiating multiple filter groups on performance under varying application characteristics.