[rules-users] From API Doc: "...This represents a working memory session where state is not kept between invocations..."

Hi guys, ( :D Personal Banner: do not forget to read my previous post :D ) I was reading the http://downloads.jboss.com/drools/docs/4.0.4.17825.GA/apidocs/index.html documentation, looking to the StatelessSession interface. On the first line we can read: "This represents a working memory session where state is not kept between invocations. " What does "invocation" stand for? What is meant for "invocation" here? Is it an insert() call? Is it a fireAllRules() call? In case of a statfullsession... is it a startProcess() call? One more doubt... Are we allowed to execute a ruleflow using\within a stateless session? Thank you again guys. Massi