An interdisciplinary team of computer scientists and EOS earth-scienceinvestigators is jointly investigating the concept of a modeling and databasesystem} (MDBS). MDBS is intended to support large-scale earth scienceinvestigations by complementing EOS-DIS in terms of support for high-levelmodeling and data management. In particular, MDBS is intended to facilitatethe iterative development of scientific models in data-intensive andcomputationally intensive applications. It is based on a simplecharacterization of scientific activity and on an advanced data model thattogether capture the essence of scientific modeling and database activities interms of large lattices of representational domains and associatedtransformations that are employed to organize scientific knowledge, data andalgorithms. A high-level, declarative modeling and database language (MDBL)that is based on this data model and on four fundamental sets of scientificoperations provides support for scientific modeling activities and for easyaccess to distributed databases of datasets and algorithms. It permits theefficient resuse of code for building new algorithms and supports key aspectsof scientific modeling activities, such as lineage and error tracking indatasets, and for the concepts of model and project. We are applying a versionof MDBS in order to solve several earth science research problems that havearisen in EOS investigations.