A GSDML file (Generic Station Description Markup Language) is provided by the manufacturer of a PROFINET IO Device and is imported into the engineering tool (e.g. TIA Portal) to integrate the device into the project.

GSDML is the PROFINET equivalent of the ".knxprod" file in KNX. It is a standardised XML format that describes the supported modules, submodules, parameters and diagnostic information of the device. It is imported once into a project or into the local library of the engineering station, and the rule of thumb is to always use the most recent GSDML version that is compatible with the device firmware.

Keep the GSDML file under version control alongside the PLC project; a silent vendor update of the GSDML can change default parameters and break a working configuration on re-import.