code: private void incrementVersion() throws FrameworkException {
  
  		// increment version on each change
  		final Long version = getProperty(SessionDataNode.version);
  		if (version == null) {
  
  			setProperty(SessionDataNode.version, 1L);
  
  		} else {
  			
  			setProperty(SessionDataNode.version,  version + 1);
  		}
  	}
docs: ----- private methods -----