Errata exists for this version of the document.
Hardware or software platforms that exist as an independent entity. UA Applications are dependent on an entity’s existence in order to perform UA services. However, the entity is not dependent on UA Applications.
Note 1 to entry: Hardware and software platforms include physical hardware, firmware, operating system, networking, non-UA applications, as well as other UA Applications. A Distributed Control System, PLC/Device, and UA Server are examples of an Underlying System.