@Override
    public String toAbsoluteUriWithCurrentBase(String uri) {
        try {
            URL base = stack.getLast().currentAbsolute;
            return URL.parse(base, uri).toString();
        } catch (GalimatiasParseException e) {
            return null;
        }
    }
@see nu.validator.xml.UriLangContext#toAbsoluteUriWithCurrentBase(java.lang.String)
src/nu/validator/xml/BaseUriTracker.java