jboss 4.5
sybase jdbc :version 6.5
jboss eclipse ide 3.1

persistence.xml
<?xml version="1.0" encoding="UTF-8"?>

<persistence-unit name="whhlega">
<jta-data-source>java:SYBASEDS</jta-data-source>



</persistence-unit>



deploy my project to jboss server will throw follow error message:
Hibernate Dialect must be explicitly set for database: Adaptive Server


could you tell me how to solve the problem ,if change the database example ms database ,is correct .