A building management system (BMS), otherwise known as a building automation system (BAS) or a building energy management system (BEMS), is a computer-based control system installed in buildings that controls and monitors the building’s mechanical and electrical equipment such as ventilation, lighting, power systems, fire systems, and security systems. A BMS consists of software and hardware; the software program, usually configured in a hierarchical manner, can be proprietary, using such protocols as C-Bus, Profibus, and so on. Vendors are also producing a BMS that integrates the use of Internet protocols and open standards such as DeviceNet, SOAP, XML, BACnet, LonWorks, Modbus or KNX. A BEMS may focus on a building’s energy use and performance rather than a wider range of building functions.