What?

HL-HDF is a high level interface to the Heirachical Data Format, version 5, developed and maintained by the National Center for Supercomputing Applications (NCSA), at the University of Illinois at Urbana-Champaign. HDF5 is a file format designed for a maximum of flexibility and efficiency and it makes use of modern software technology. Briefly, HDF5 has the following characteristics:

• Platform independence. For example, an array of native floating point values written on one platform will be automatically identified, byte-swapped if necessary, and returned as an array of native floating point values on another platform.
• Built-in compression using the free ZLIB compression library. ZLIB is well-known as the compression used in the gzip package and it is robust and efficient.
• Flexible. HDF5 offers the ability to store virtually any kind of scientific data.

The HDF5 project URL is http://hdf.ncsa.uiuc.edu/HDF5/ and links are available to source code, software and copious documentation.

HL-HDF is designed to focus on selected HDF5 functionality and make it available to users at a high level of abstraction, the idea being to make the management of their data easier. A strong effort has been made to ensure that this functionality, although a limited subset of HDF5 functionality, provides a general and flexible set of tools for managing arbitrary data. Like HDF5, HL-HDF is meant to be used on different computer platforms. In practise this means different flavours of UNIX and NT. HDF5 may work on other systems, like the Mac, DOS and VMS, but NCSA does not support them (yet) which means that HL-HDF does not support them either. This is not to say that they will not work on these platforms, however.

Binary tools available with HDF5 will work with files written with HL-HDF. For example, `h5dump' can be used to determine the contents of an HDF5 file written with HL-HDF. A few test programs are included with HL-HDF which can read/write raw data to/from HDF5 files. These test programs may be useful to users who do not wish to write their own routines using the functionality available in HL-HDF, but would prefer to rely on a simpler encoder and decoder. These programs can also be used as examples of how to write routines using HL-HDF.

HL-HDF is free software and it may be used used by anyone according to SMHI's and NCSA's copyright statements containined in this document. Users are encouraged to report their feedback to the author, and to contribute to its development.