Web Services in Building Automation with focus on BACnet/WS

Currently, there exist two major challenges in the scope of Building Automation System (BAS) integration. First of all the integration of building automation subsystems from different vendors is difficult due to still existing proprietary solutions. The second challenge is the integration between BASs and enterprise applications. Web services have been proven to be capable of solving both of these problems. This paper outlines the three most common web services based technologies in building automation, i.e., OPC Unified Architecture (OPC UA), Open Building Information Exchange (oBIX), and Building Automation and Control Network Web Services (BACnet/WS). In the main part of this paper BACnet/WS is discussed in detail including the specified data model, attributes and services. Finally the results of a BACnet/WS performance study are presented.