The CCP Data Model for macromolecular NMR is intended to cover all data needed for macromolecular NMR spectroscopy from the initial experimental data to the final validation. It serves for exchange of data between programs, for storage, data harvesting, and database deposition. The data model proper is an abstract description of the relevant data and their relationships - it is implemented in the modeling language UML. From this CCPN autogenerates interfaces (APIs) for various languages, format description and I/O routines, and documentation.