The graphical user interface is the gateway into the modeling environment. It presents the user with a familiar Motif style look and feel, and guides the user through the modeling session through the use of hierarchical menus. The main window remains on the screen throughout the session.
The models menu presents a list of available models. Models have been grouped into 4 basic categories at present: Climate, Vegetation, Soil, and Radiation. A choice of category reveals a menu of the actual models, such as the Zelig model of forest population dynamics.
Selection of a specific model results in the display of a window which will guide the user through the setup process for that particular model type. The first step is choice of a predefined configuration file for the initial values of parameters. "Standard" is a safe choice for model stability, but may not represent the best starting point for the simulation planned. The user may select any other configuration file through the file-open option.
The preliminary configuration may now be customized by the user through panels which handle the input parameters for this model type. In the case of Zelig, there are two available panels, "Initialization" and "Site-Specific".
For the site-specific panel, there are two input methods per item: mouse-driven slider or a keyin window. The slider ensures that the specified value will not exceed the limits imposed by the chosen configuration file. However, the keyin window is there for the express purpose of allowing the user to go under or over those limits, if that is what the user really wants to do. If the user changes values, those values will be checked for consistency with the underlying constraints in the configuration file when the OK button is pressed. If, for instance, the user has elected to exceed the upper limit on an item, a warning window will pop up and offer the user several choices for resolving the situation.
In general, the user may elect to edit the choice so that it will conform to the existing constraints, undo the parameter in question so that the previously "legal" value is restored, or override the violation, which means that the user may go ahead and send that value to the model. The results after an override are difficult to predict and may include a core dump, however! This feature reflects the underlying philosophy that the function of the software surrounding the models is merely to facilitate the user's interaction with the models, not to limit or control it. The novice user will find it easy to "try out" a model in a well-tested configuration, while the expert user is free to push the models to their boundary conditions and beyond.
The user may set up desired dynamic displays and reporting of results via the "View" menu. Each model has an associated list of supported attributes. These are the state variables, fluxes, and key driving variables that are "made public" for examining what the model predicts, how it behaves, and why. These attributes may be selected for display or file output via "View". Three basic output types are supported: file, graphical display, and diagnostic.
Graphical display allows the display of one or more attributes in a variety of graphical formats. The stripchart display corresponds to the old real-time analog display device that produces a continuous display of a parameter versus time. Unlike the analog version, up to six parameters can be displayed in overlay fashion to allow easy contrast and comparison of attributes. The file option reports an attribute at regular intervals or at a breakpoint. Diagnostic reporting is intended to support more intense examination of the modeling data space. Once the reporting time specification has been made (every step for graphics, user-specified for file or diagnostic) the report specification procedure is basically the same. An attribute selection box will appear.
A temporal averaging window will pop up which asks the user to choose between instantaneous values or averaged (since the last reporting time) values. After this choice has been made, the user will be prompted for spatial averaging information.
Once the report has been completely defined, it will be registered with the modeling environment and added to a list for the user's record.
Once the user has finished defining reports for this model, the file menu is used to return to the main panel, and allow access to the models menu again. Continuing in this manner, the user may configure any number of models, either different types of models or multiple versions of a single model type, or a combination thereof. The list of models will appear under the "Models: Configured Models" menu. If a model is selected from this menu rather than from the model category hierarchy, then the user can alter the configuration or view for a previously added model.
When the user has finished adding/replacing/deleting models from the modeling environment, the actual simulation may be started via the "Control" menu. The models may be run to completion, as indicated by the framework simulation time, or to the first breakpoint as specified in the view setup. In either case, the clock will start ticking, and the elapsed time will be indicated via a graphical display. Any graphical reports requested will begin their display.
The user may interrupt the simulation by suspending the simulation. This allows more reports to be added, or even new models. Any graphical displays will also freeze upon a suspend request, so this makes close scrutiny of the displays possible. The user may also control the clock speed to slow down the simulation clock if the results fly by too quickly. Before exiting from the main panel file menu, the user may save any changes made to the configuration files so that work may be continued at a later time.
