Three years ago an ASHRAE committee was formed to develop an open and interoperable standard for the description of the control logic used in building control systems. The committee started with the work done by the DOE funded "Open Building Control" project (see obc.lbl.gov) and reviewed existing commercial control sequence languages.

The draft standard contains definitions for a Control Description Language (CDL) which is defined in the modeling language "Modelica". It also has a version of CDL called the Controls eXchange Format (CXF) which is defined using JSON-LD. CDL and CXF share the definitions for over 130 "elementary functions" such as "Add", and "PID".

CDL and CXF will enable sharing control logic in a machine readable form from design to deployment and between control systems.

The public review period runs from 2/2/2024 - 3/18/24. The draft document and a link to enter comments can be found at https://osr.ashrae.org/ . The project committee is encouraging public review and comments.