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Current solutions to these problems focus on fancy icon-based graphical user interfaces that depict the cryptic 
proprietary commands. While the GIS modules usually reflect the task flow from data input, via storage, 
manipulation, analysis to data output, the individual operations are data-centered. It is here that the project 
"Virtual Geographical Information System" (VGIS) derives its justification. The purpose of VGIS is to create 
a universal graphical user interface (GUI) that can be used with any current GIS. VGIS' graphical front-end 
builds upon a limited set of universal data structure-independent analytical GIS operations that allow the user 
to build processing models - transformations between different data structures are to be executed automati 
cally. The graphical user interface works like a general purpose flow charting tool that depicts the workflow 
consisting of a number of processing steps to be applied to the input data. This processing plan can be created 
and edited interactively using a mouse. The plans can be saved just like macros, to be used later on with other 
data. The visual programming character facilitates easy adaptations to changing needs. A first implementation 
of VGIS runs on the public domain GIS GRASS coordinated by OGI at USACERL. Current development 
concentrates on writing an interpreter for the vector GIS Arc/Info from ESRI, Redlands, (CA), while the basic 
research focuses on a more umversal interface to the Open Geodata Interoperability Specification (OGF 
1993). 
2 THE UMVERSAL GIS OPERATIONS 
Almost all GIS-related research is data-centered. Even human factor studies usually take the dichotomy of 
raster- versus vector-GIS for granted and analyze GIS usage either on a key-stroke or on a task level (Turk 
1992, Medyckyj-Scott and Heamshaw 1993). In neither case the original purpose for using a GIS in the first 
place is taken into account. If a GIS is employed for assignments that go beyond mere data repository chores, 
then the operations on data become at least as important as the data themselves. Investigation of these 
operations in a processing model context has been neglected until very recently (Albrecht 1994, Voisard 1995, 
Hamilton and Worboys 1996). 
Many GIS users possess expert-level knowledge in the application field in which the GIS is to be utilized, but 
have neither the time nor desire to learn the technical intricacies of a specific system. The user's overall goal 
should not be the mastery of a new system but more productive interaction with geographic information. An 
obvious response is to provide an user interface which alleviates the need for specialized training. This user 
interface should aim at enhancing user interaction with geographic information and with geographic problem 
solving rather than with systems. Much of the user interface problem is therefore not a programming problem 
but a conceptual problem (Mark and Gould 1991). Frank (1993) illustrates the crucial importance of the user 
interface for the usability of a GIS with the following lines: "The user interface is the part of the system with 
which the user interacts. It is the only part directly seen and thus 7 s' the system for the user."