hydrologic model discussed in this paper), we need a system that keeps track of the process meta 
data and of the process state. A CAD framework offers some promising features in this regard, 
but more research is needed to address more advanced requirements such as distributed data and 
computing. The experience gained in this research framework shows that an integration of a com 
plex environmental model with CIS and scientific visualization tools is feasible, and that a more 
profitable use of the model could be made, especially in the case of having to perform complex sets 
of simulations (many sites, many events, etc.). 
Before embarking on any integration effort, it is important to define what is to be expected from 
the final system. The intended users and the frequency and intensity of use of the integrated tool 
are just a few of the criteria that will determine the type of integration most appropriate for a given 
application. The final choice will often be a compromise between the cost and time of development 
and the gain in performance that is achieved by the integration. 
Acknowledgments This research has been carried out with the financial support of the Eu 
ropean Environment Research Programme (contract EV5Y-CT94-0446), the European AVICENNE 
Research Programme (contract AVI-CT93-2-073), and the Sardinia Regional Authorities. 
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