To open the applet click on the Test datanames pin. If you do not have this pin on your start screen you can add it using the new pin function.
Enter in the dataname field the dataname you want to test and click on Test. Below the form apears an analysis of the dataname. It shows step by step how the dataname is transformed to the final value. If you've made a mistake in writing the dataname, it's directly clear in what part of the dataname the problem occurs.