US Patent 8682921 Query engine for building management systems

A computer-implemented system for facilitating cross-subsystem queries of a plurality of building automation subsystems includes a first database storing a logical model for a building automation system. The system further includes a second database storing information for the plurality of building automation subsystems. The second database relates information for the plurality of building automation subsystems based on the logical model of the first database. The system also includes a query engine configured to decompose a cross-subsystem query received from an application into a plurality of subsystem queries using the information of the second database.