https://community.appian.com/discussions/f/rules/1270/appian-release-6-6-1-in-an-if-statement-we-used-the-function-isusernaAppian Release 6.6.1 In an if statement we used the function isusernametake for the conditional. The following exception was thrown: The expression function &#39;isusernametaken(&quot;fleung&quot;)&#39; (user=fleung, exprId=690) could not be evaluated: JAXB failure tryingen-USTelligent Community 12https://community.appian.com/thread/4395?ContentTypeID=1Fri, 27 Sep 2013 11:06:06 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:c9665adc-27b1-4742-8098-8493fcd3561cshelzleTry to restart JBoss. If that fixes the error your problem relates to duplicate libraries within plugin jars. Check all jars for libraries that are also delivered by Appian. Appian support can help you on this.<div style="clear:both;"></div>https://community.appian.com/thread/4387?ContentTypeID=1Fri, 27 Sep 2013 01:41:42 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:917b5a46-f1b3-46e0-8962-6162ca0b5ba2Matt LuoThis error will be thrown if there is a data casting error. Please be sure the input is the expected data type.<div style="clear:both;"></div>https://community.appian.com/thread/4384?ContentTypeID=1Thu, 26 Sep 2013 23:56:22 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:6d20cc7c-a900-464c-b24c-4f2a846b9134felixlhmmm, that is an unfortunate carry over<div style="clear:both;"></div>https://community.appian.com/thread/4383?ContentTypeID=1Thu, 26 Sep 2013 23:55:24 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:9da186c2-c6a7-45a1-ada5-db8cd4ca5300felixl...assLoader. <br /><br />This is the first I&#39;ve seen of this error. If anyone has experienced a similar error before your input is greatly appreciated. Thanks.<div style="clear:both;"></div>