Data Access Object design pattern specification to enable {@link Session} access to an EIS (Enterprise Information System). It provides your four typical CRUD methods: {@link #create}, {@link #readSession(java.io.Serializable)}, {@link #update(hunt.shiro.session.Session)}, and {@link #remove(hunt.shiro.session.Session)}. <p/> The remaining {@link #getActiveSessions()} method exists as a support mechanism to pre-emptively orphaned sessions, typically by {@link hunt.shiro.session.mgt.ValidatingSessionManager ValidatingSessionManager}s), and should be as efficient as possible, especially if there are thousands of active sessions. Large scale/high performance implementations will often return a subset of the total active sessions and perform validation a little more frequently, rather than return a massive set and infrequently validate.