Bojan, I don't understand exactly what you're trying to do. But it's very simple to add parameters dynamically to the parameter database, just use database.set(new Parameter("my-parameter"), "my-value") It's exceedingly rare to need to do this though: in fact ECJ does it only once (for master-slave communication). If you're thinking of setting parameters dynamically, you're almost certainly going down the wrong road. Sean On Jun 30, 2013, at 4:03 PM, Bojan Janisch wrote: > I've search in the manual, but there was only a small part which describes the creation of parameters. > Does someone got a simple example of how to get a specific parameter e.g. custom inputfolder at > evaluation of a GPTree?