#2 Optimize Message Text Missing Rule Verification

dmnverifierapi/src/main/java/de/unikoblenz/fgbks/core/dmn/verification/verifier/impl/MissingRuleVerifier.java

@@ -49,12 +49,13 @@ public class MissingRuleVerifier extends AbstractVerifier {
     for (VDmnRule missingRule : missingRules) {
       StringBuilder sb = new StringBuilder();
       sb.append(templateDecision(dmnDecisionTable.getDmnDecision()));
-      sb.append("The following rule is not defined: {");
+      sb.append("The following rule is not defined: { ");
       sb.append(
           missingRule.getDmnInputValues().stream()
               .map(v -> v.getBoundary().getParsedText())
-              .collect(Collectors.joining("), (")));
-      sb.append("}");
+              .map(s -> s.isEmpty() ? "-" : s)
+              .collect(Collectors.joining(" / ")));
+      sb.append(" }");
 
       vreFactory.addElement(VerificationResultEntryElement.create(dmnDecisionTable));
       vreFactory.addToEntry(VerificationClassification.WARNING, sb.toString());