thanks, shekharv yes, org.jbpm.pvm.internal.hibernate.DbSessionImpl is an implementation of org.jbpm.pvm.internal.session.DbSession, but maybe you don't understand me(my english is so poor). what I don't understand is that: the methods #svae/#delete/#flush/... in DbSessionImpl are delegated forward to the corresponding method(same method name) call of org.hibernate.Session, it seems the author would like to see DbSession rather than org.hibernate.Session in this program, but why make it internal? and, in modules like pvm/jpdl/enterprise, I found lots of references to org.hibernate.Session directory(in some commands, activities, etc.), which are retrived from the Environment, why not using DbSession instead? View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4238659#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...