def meaningfy(self):
            fs = []
            for k,v in self._functions.items():
                kk = k
                if isinstance(v, dict):
                    if v.has_key("additionals"):
                        for a in v["additionals"]:
                            kk = "%s+%s" % (kk, a)
                    if v.has_key("tree_key") and v["tree_key"] is not None and kk == 'categories':
                        self._params["tree_key"] = v["tree_key"]
                fs.append(kk)
            fs = ";".join(fs)
            url = "%s.%s" % (fs, self._format)