The scientific world is evolving to require more collaboration among different institutions and disciplines. Understanding long-term changes in the Earth environment, for example, requires models that integrate disciplines such as meteorology, oceanography, hydrology (rivers and groundwater), soil science and geology. During the past 15 years, scientists have started sharing data using FTP and software on the Internet, but collaborative work and more routine data sharing require a new kind of scientific software.Distributed object technology is a software technique for supporting programming language references to objects on remote computers. Invoking methods of remote objects is similar to the remote procedure call (RPC) capability of Unix. Programs on any number of computers may contain references to each other's objects, so