The Interactive programme runs a simple command line conversation which allows ADQL to be typed in and echoes back useful information on what the parser produces.
The basic display is a pretty print of the intermediate XML, or error messages if the parse fails for any reason. It can be augmented by passing in a style sheet, which will be applied to the XML.
There is an option to pass in metadata so some metadata processing can be simulated.
Switch tracing on in Log4J for extensive tracing of the syntax call path. Really useful if you are debugging syntax.