if(rule.arity() == 1) {
GdlLiteral literal = rule.get(0);
if(literal instanceof GdlRelation) {
//Check that it really is the true form
SentenceForm trueForm = nextForm.withName(GdlPool.getConstant("true"));
if(trueForm.matches((GdlRelation) literal)) {
GdlSentence head = rule.getHead();
GdlSentence body = (GdlSentence) literal;
//Check that the tuples are the same, and that they
//consist of distinct variables
List<GdlTerm> headTuple = GdlUtils.getTupleFromSentence(head);