Every automation station contains all the data necessary for stand-alone operation, including, e.g., date and time, calendar function blocks and Notification Class function blocks. The system functions of individual automation stations do not depend on a central server.
The System View and the Program View are based on the automation station, that is, each object (block, BACnet data object) belongs to a specific automation station. These objects are called local objects. This form of representation is adequate for most elements of a physical plant, e.g., for the supply air temperature or the set point of a ventilation system.
However, certain data objects need to be visible in identical form in some or all the automation stations of a site. These objects are called global objects. Global objects let you centrally change parameters, which are then distributed to all automation stations.
Local objects are individual and unique objects which exist only once on a particular automation station in the system. Most application-related objects are local objects. When local objects are required, such as the outside temperature in several automation stations, access to this data must be configured or programmed explicitly with function blocks (such as analog, binary and multistate inputs, or grouping in the room management system) and referencing.
Global objects are data objects which exist simultaneously on each automation station at the automation level. Global objects are always global within a given site. Global objects are engineered in Xworks Plus (XWP).
Global objects are compiled in a global chart. There is exactly one global chart per site. You can modify global charts, save them in the tool's library folder, and copy them to other projects.