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Figure 4: The Design System User Interface showing a part of the design flow for topographic 
analysis. 
framework itself, execution of these tools can be done by simple system calls. 
Integrating these small FORTRAN programs in the XELSIS framework simplifies the work of 
the modeler. Invocation of the tools becomes completely automated, thus eliminating the possibility 
of user errors (the invocation method is hidden and the order in which the routines are to be run is 
visually and conceptually determined by the flow paradigm). A user can easily check which DEMs 
have been analyzed, and the status of the analysis for each of these DEMs. Intermediate results 
are saved, and for final output not only the original inputs but also all intermediate results can be 
examined in a very straightforward way. . 
Integration of topographic analysis tools is but the first step in our overall hydrologic application. 
Different users can develop different pieces of the complete flow, and can take advantage of each 
integration step to simplify their work. There is no need to wait until the integration of all tools 
is completed, as would normally be the case in a tight integration approach. Further integration 
of our hydrologic modeling process using XELSIS is in process. We will be assessing the ease of 
use and efficiency of this framework, and investigating its ability to integrate or encapsulate highly 
interactive visualization tools and to handle distributed configurations wherein data, tools, and end 
users may reside on different computers. 
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6.0 CONCLUSIONS 
For simple applications, shell scripting in combination with an appropriate graphical user in 
terface (GUT) can provide an effective integration platform. For more complex processes (like the