In order to further understand the theory of JCR and the API, please refer to some external documents about this standard:
Roy T. Fielding, JSR 170 Overview: Standardizing the Content Repository Interface (March 13, 2005)
Benjamin Mestrallet, Tuan Nguyen, Gennady Azarenkov, Francois Moron and Brice Revenant eXo Platform v2, Portal, JCR, ECM, Groupware and Business Intelligence. (January 2006)