private static boolean hasSingleOccurrenceInPremise(FormulaVariable variable) { if (logger.isTraceEnabled()) logger.trace("Occurrences for variable: " + variable.toLongString()); int relationalPremiseOccurrences = variable.getPremiseRelationalOccurrences().size(); int nonRelationalOccurrences = variable.getNonRelationalOccurrences().size(); return relationalPremiseOccurrences + nonRelationalOccurrences <= 1; }