The XSD defines a data structure for an unambiguous, easy-to-use, safe and uniform exchange of fundamental physical constants and mathematical constants in a machine-readable data format. The data elements for constants are defined in the Digital System of Units (D-SI) metadata model from the EMPIR project 17IND02 SmartCom. The development of the data structure was based on an own analysis of minimum requirement for transfering the data of fundamental physical constants "as are" provided by CODATA into a machine-readable form. Furthermore, the considerations for the transformation comprise traceability to the original CODATA values. The availability of machine-readable data of fundamental physical constants that can easy be accessed by software and that are traceable to a international accepted definition is essential for various areas of metrology where the International System of Units (SI) is of key-importance.

The development of the unified meta data format for the exchange of measurement data in ICT applications and its implementation using XML is part of the research project EMPIR 17IND02 (title: SmartCom). This project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme.

{"references": ["Web ressource XML scheme for fundamental constants: https://www.ptb.de/si/codata/codata.xsd"]}