Computational science is a rapidly growing multidisciplinary field that uses advanced computing capabilities to understand and solve complex problems. So far, grid computing has gained some maturity with respect to the actual computation. However, the management of data in grid networks is still a very immature area. In this paper, we present DASCOSA (database support for computational science applications), which consists of a) a grid database management system based on the peer-to-peer paradigm (POR-DaS), and b) a semantic layer that provides seamless access to the heterogeneous sources in the data grid. We present the architecture of PORDaS, and the design of the semantic layer that is under development