Changes to the hardware, software, or firmware components of the system or the operational procedures related to the system can have potentially significant effects on the security of the system. Therefore, organizations permit only qualified and authorized individuals to access the system for the purpose of initiating changes. Access restrictions include physical and logical access controls, software libraries, workflow automation, media libraries, abstract layers (i.e., changes implemented into external interfaces rather than directly into the system), and change windows (i.e., changes occur only during specified times).