The ARION system provides basic e-services of search and retrieval of objects in scientific collections, such as, data sets, simulation models and tools necessary for statistical and/or visualization processing. These collections may represent application software of scientific areas, they reside in geographically disperse organizations and constitute the system content. The user, as part of the retrieval mechanism, may dynamically invoke on-line computations of scientific data sets when the latter are not found into the system. Thus, ARION provides the basic infrastructure for accessing and producing scientific information in an open, distributed and federated system. More advanced e-services, which depend on the scientific content of the system, can be built upon this infrastructure, such as decision making and/or policy support using various information brokering techniques.