A Modular Spatial-Temporal Modeling Environment for GIS

Development of an open source modeling environment for use with spatial-temporal data in a Geographic Information System (GIS) is presented. MapWindow GIS, a free and open source desktop GIS, has been used extensively in watershed modeling and is the underlying engine of the U.S. EPA BASINS system. To date, legacy versions of MapWindow have lacked an integrated modeling environment suitable for linking together geospatial and temporal independent processes at a granular level. New developments in the open source MapWindow GIS 6 project have created the basic framework for an extensible modeling environment. This new modeling environment allows users to easily create models which can take advantage of spatial and temporal data objects and analytical tools. The design approach involves the extensive use of interfaces which are essentially skeleton programming tools that detail how an object programmatically interacts with other objects, but not necessarily how it works internally. By using interfaces, the new MapWindow GIS modeler makes it relatively simple to take existing modeling processes, wrap them in an appropriate interface, and execute them as part of a more complex model. By using interfaces any one component of the modeler can be replaced by any other object that implements the same interface. The central underlying design consideration of the newest version of MapWindow GIS was to keep the entire project as modular as possible. The developed modeler uses a simple interface to define how processes or tools should interact with other model components. The tool interface requires developers to specify a number of simple methods on their tool's object which are then called by the model when the tool is loaded. Developers need not spend time designing the user interface for their tool as it is automatically generated by the modeler when their tool is instantiated. Because all tools in the MapWindow modeler must implement the same interface, developers wishing to use a tool directly in their own application need not add the modeler if they do not so desire. By adding a reference directly to the tool they want to use they can gain access to all of the same methods that would be exposed to them if they worked with it through the modeler. MapWindow GIS 6 and the modeler are entirely developed using the Microsoft. NET Framework which allows it to be run on a variety of operating systems including Windows, Linux or OS X (via the Mono compiler).