Observations

Methods extension, complexType, sequence and etc. have declaration like this:

 
public static XTExtension extension(XTNode... nodes);

Than we use

import static xsdgraph.model.XTUtil.*;

Also C-strXXX like style for setting arbitrary number of attributes:

public class XTElement {
    public XTElement minOccurs(int value) {
        minOccurs = value;
        return this;
    }
}