Agile prerequisite and dependent stories

Is there any ServiceNow functionality that is associated with adding "prerequisite" or "dependent" stories?  Or are these stories used for documentation purposes only?  It doesn't appear that entering these stories controls or forces a conduction upon the original related story.  For example, I would have thought that adding a dependent story would mean that the original story can't be closed until the dependent story is closed but that doesn't appear to be the case....