This International Standard specifies the characteristics of software and functions used in Building automation and control systems as well as a method for documentation of the design. It gives guidelines for the engineering. It specifies a template for documentation of plant/application specific datapoints and functions, called BACS function list in annex A. The informative function block examples explain a method to display the referenced functions in system documentation; they do not standardize the method for programming functions and applications. This International Standard covers the following: Requirements and definitions regarding BACS and application software, generic function types for plant/project specific applications and engineering functions for building controls and operations. It provides communication functions for the integration of other dedicated special system processes. The functional requirements in this part of the standard are subdivided as follows: • — System management and application software: This clause describes the requirements for plant independent system and human system interface programs related to a project, including the operating system. This standard does not dedicate the following system functionality to any particular hardware, e.g.: o — system diagnostics, watchdog, redundancy, time keeping, access control, log lists; • o — point identification, event message handling, print control; o — database, statistics, data archiving, remote access; o — system communications. • — Human system interface (HSI), point information presentation, graphics, alarms, time scheduling • — Engineering process and tool software: This clause describes the requirements for configuring of the hardware and control strategies, the system management, and the commissioning process. • — BACS application processing programs and plant/application specific function types: This clause describes the requirements for plant, application, and / or project specific functions and a method for the documentation of a project. The functions are subdivided into the following types: o — input and output functions; • o — processing functions; o — management functions and required communications; o — operator functions. This International Standard defines a method for creating the procurement specifications containing all essential elements required for the operational functioning of a BACS. The successful installation and operation of a BACS requires that its procurement be based on a complete specification with accurate functions. The standard provides a template called the ‘BACS function list’ that can be found in annex A (normative). Its purpose is to determine and document the options for plant / application specific functionality. Further explanations can be given in form of plant/control descriptions, control flow chart diagrams, and plant/control schematics. Examples are given in annex B (informative). The exact specifications will be project-specific. Information about the standardized functions is given in the form of informative examples as function-blocks, textual, and graphical descriptions in 5.5. It is recognized, that functions can be described and implemented in many different ways, depending on: • — climatic differences; • — cultural and regional differences; • — national regulations.