The metadata makes the difference from a normal CAD drawing to a BIM object. A BIM object typically contains geometric, descriptive and information about the connection. The metadata are properties that further describe / classify the object (such as performance, order number, weight or material). This data is needed to realize the BIM process.
At the moment, there is no set of rules that describes which data are needed for a BIM object in detail. In Germany this will be standardized in the future via the VDI 2552. To allow software programs to work with a BIM object without data loss at present, there is also a lack of a clear definition of terminology, such as “rated output”. This identifier for the terms (via a unique ID) is currently defined as part of the creation of ISO 16757 via the buildingSMART Data Dictionary (bSDD), e.g. Rated output heat generator [kW] = ID: 4711.
Until the definitions in bSDD are applicable, BDH and VDMA have agreed to create a transitional definition based on VDI 3805. For more information, please refer to the Excel Sheets