Unable to build EntityManagerFactory while running standalone jBPM Project.

Issue

We are trying to create to a JBPM Project with on JBDS 7.1.1, but we are facing following error:

Exception in thread "main" javax.persistence.PersistenceException: [PersistenceUnit: org.jbpm.persistence.jpa] Unable to build EntityManagerFactory
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:930)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:904)
    at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:72)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:63)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:47)
    at org.jbpm.runtime.manager.impl.DefaultRuntimeEnvironment.init(DefaultRuntimeEnvi

This error is coming when i am creating a project with the "Human Task node", but when i am creating a simple(Without Human Task Node) jbpm project it will create and run successfully.