After an RGG object has been loaded successfully from an XL file, its public methods are made available in the RGG toolbar. Each method appears twice: In the list prefixed with Apply, a click invokes the method once, in the list prefixed with Run, a click starts the repeated invocation of the method. To stop this loop, click the Stop button in the toolbar. Initially, buttons for the first method are accessible immediately; to see a button list for the other methods, you have to click on the small arrow at the right button border.

Normally, RGG methods cause the application of graph grammar rules to the scene. This is the case for the examples provided at GroIMP's web page, and you should try these examples to get familiar with GroIMP's RGG facilities.

The XL source code of a relational growth grammar can be edited in GroIMP's internal text editor, just double-click on the XL file in the file explorer. Whenever modifications of an XL file are saved using the text editor's Save button, it is recompiled, and the RGG object becomes reinitialized. Compilation errors are shown in the message panel and contain hypertext links to their source code locations.

If the filename ends in .rgg instead of .xl, a simplified syntax is used. In this case, the most common import statements are implicit, as is the enclosing RGG-class declaration.