1. A method of creating a validation policy, the method comprising: generating a validation policy for use with a business rule engine (BRE), the BRE comprised in a computer associated with an application server system; generating an assertion rule comprised in the validation policy to create an enumerator; generating an advancing rule comprised in the validation policy that asserts the enumerator to the BRE as a fact; and generating one or more evaluation rules comprised in the validation policy where each of the one or more evaluation rules comprises a check format function and an error formatting function; wherein the check format function is configured to use an XPath statement to return one or more data values from the enumerator and further comprises one or more validation patterns and a corresponding one or more validation functions that are configured to verify whether the one or more data values returned correspond with a pattern comprised in one of the one or more validation patterns and the one or more validation functions; and wherein the error formatting function is configured to, in response to one or more of the one or more data values failing to be verified by the check format function: generate an error message comprising the one or more of the one or more data values that failed to be verified and an indication of which of the one or more validation patterns that was failed; and generate a computer interface to display the error message.