For years, the end users in the controls industry have struggled with the complexities of multivendor building automation and control systems. Proprietary, vendor-exclusive hardware, software and communications protocols have created closed systems that present integration and operation/maintenance challenges. Several open standards and associated technologies, most notably BACnet® and LONWORKS®, offer the potential for open multivendor systems. However, realizing this potential requires correct design and implementation (as does any system whether it be open or closed), which is not a trivial task. It is possible to design and implement these new technologies and still retain a closed system.