  For decades now, scientific data volumes have experienced relentless,
exponential growth. As a result, legacy astronomical data formats are straining
under a burden not conceived when these formats were first introduced. With
future astronomical projects ensuring this trend, ASTRON and the LOFAR project
are exploring the use of the Hierarchical Data Format, version 5 (HDF5), for
LOFAR radio data encapsulation. Most of LOFAR's standard data products will be
stored using the HDF5 format. In addition, HDF5 analogues for traditional radio
data structures such as visibility data and spectral image cubes are also being
developed. The HDF5 libraries allow for the construction of distributed,
entirely unbounded files. The nature of the HDF5 format further provides the
ability to custom design a data encapsulation format, specifying hierarchies,
content and attributes. The LOFAR project has designed several data formats
that will accommodate and house all LOFAR data products, the primary styles and
kinds of which are presented in this paper. With proper development and
support, it is hoped that these data formats will be adopted by other
astronomical projects as they, too, attempt to grapple with a future filled
with mountains of data.

Instrumentation and Methods for Astrophysics;Cosmology and Nongalactic Astrophysics