The session object is a sequence of command nodes that represents a user session from login to logout. The command nodes hold information about how the commands were instantiated and links to the affected objects. See section 8.5 for a complete list of command node attributes and links.
By storing a session as versions of the same object, we use the existing temporal history to represent the succession relation and the edit history to represent the precedence relation. See figure 12 for an example.
: How the example history in figure