12. A computer-implemented method for facilitating cross-subsystem queries of a plurality of building automation subsystems, comprising: receiving a cross-subsystem query from an application; accessing a fact database that stores instance values for the plurality of building automation subsystems and a logical type for each of the stored instance values, wherein the logical type identifies a particular attribute of an ontological model described by the stored instance value and represents, in a flat format, a portion of the ontological model that provides semantic type information for the stored instance value; parsing the logical types in the fact database to obtain the semantic type information for the stored instance values; using the obtained semantic type information to identify one or more of the stored instance values relevant to the cross-subsystem query without requiring access to another database; recognizing that the identified instance values are provided by more than one of the plurality of building automation subsystems; and decomposing the cross-subsystem query into a plurality of subsystem queries using information from the fact database.
12. A computer-implemented method for facilitating cross-subsystem queries of a plurality of building automation subsystems, comprising: receiving a cross-subsystem query from an application; accessing a fact database that stores instance values for the plurality of building automation subsystems and a logical type for each of the stored instance values, wherein the logical type identifies a particular attribute of an ontological model described by the stored instance value and represents, in a flat format, a portion of the ontological model that provides semantic type information for the stored instance value; parsing the logical types in the fact database to obtain the semantic type information for the stored instance values; using the obtained semantic type information to identify one or more of the stored instance values relevant to the cross-subsystem query without requiring access to another database; recognizing that the identified instance values are provided by more than one of the plurality of building automation subsystems; and decomposing the cross-subsystem query into a plurality of subsystem queries using information from the fact database. 20. The computer-implemented method of claim 12 , further comprising: measuring a variable state or condition within a building space using one or more sensors, wherein at least one of the stored instance values is provided by the one or more sensors; generating a control signal at a controller using information provided by the one or more sensors; and operating one or more BAS devices configured to affect the measured variable state or condition using the control signal from the controller.