There is no standard way in astronomy to represent digital spectroscopic data. We present requirements for a standardized 1dimensional spectral data model for use in the Virtual Observatory. We discuss the different kinds of spectra and the different observables used, as well as the appropriate instrumental calibrations. Our model is intended as a special case of an n-dimensional model for image and spectral data, and would incorporate the FITS spectral WCS proposal for coordinate descriptions. The problem of describing spectral data is closely related to the problems of defining bandpasses and photometric calibrations, as well as of abstract instrument descriptions such as spectral responses and efficiencies.