+
+ public String toPQF(Properties config) throws PQFTranslationException {
+ return ("@" + opPQF() +
+ " " + left.toPQF(config) +
+ " " + right.toPQF(config));
+ }
+
+ // represents the operation for PQF: overridden for CQLProxNode
+ String opPQF() { return op(); }
+
+ abstract String op();