Currently, there are 3 levels of gbXML certification:
Level 1 compliance involves validating that a gbXML file is a well formed XML (per the W3C ISO Standard) and also conforms to the gbXML XSD (from gbXML versions 0.37 to 6.01, depending upon which version the software tool currently exports).
Level 2 compliance involves validating a gbXML file against 8 to 10 geometric “test-cases” that are based upon ASHRAE Research Project 1468, “Development of a Reference Building Information Model (BIM) for Thermal Model Compliance Testing”. This research project contains the rules and guidelines for mapping a given Building Information Model (BIM), created with BIM authoring tools such as Autodesk Revit, into a Building Energy Simulation (BES) description for energy simulations. The test cases provide the instructions for a software vendor to create specific geometric models that are then submitted to an online validator hosted at gbXML.org that checks for compliance At this time, only NREL’s Open Studio software tool is validated for Levels 1 and 2 compliance.
Level 3 compliance has yet to be fully defined. However, Level 3 does involve certain levels of vendor tool automation that goes far above and beyond Levels 1 and 2 compliance. We are currently working with Autodesk to better define Level 3 compliance.