Newsletter #29

February 18, 1998

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CONTENTS

• HDF5 release 1.0.0a
• European mirror site of HDF

HDF5 version 1.0.0a is now available, and can be downloaded from the HDF ftp server (hdf.ncsa.uiuc.edu), in the directory: https://support.hdfgroup.org/pub/dist/HDF5/

The documentation for this release can be found at:http://hdf.ncsa.uiuc.edu/nra/BigHDF/

What is the HDF5 library?

HDF5 is a new, experimental version of HDF that is designed to address some of the limitations of the current version of HDF (HDF4.1) and to address current and anticipated requirements of modern systems and applications.

This HDF5 library is not complete, but it should be sufficient to show the basic features of HDF5. We urge you to look at it and give us feedback on what you like or don't like about it, and what features you would like to see added to it.

Why HDF5?

The development of HDF5 is motivated by a number of limitations in the current HDF format, as well as limitations in the library. Some of these limitations are:

• A single file cannot store more than 20,000 complex objects, and a single file cannot be larger than 2 gigabytes.
• The data models are less consistent than they should be: there are more object types than necessary, and datatypes are too restricted.
• The library source is old and overly complex, does not support parallel I/O effectively, and is difficult to use in threaded applications.

When complete HDF5 will include the following improvements:

• A new file format designed to address some of the deficiencies of HDF4.1, particularly the need to store larger files and more objects per file.
• A simpler, more comprehensive data model that includes only two basic structures: a multidimensional array of record structures, and a grouping structure.
• A simpler, better-engineered library and API, with improved support for parallel I/O, threads, and other requirements imposed by modern systems and applications.

limitations of the current library:

The prototype release includes most of the basic functionality that is planned for the HDF5 library. However, the library does not implement all of the features detailed in the format and API specifications. Here is a listing of some of the limitations of the current release:

• Attributes for data objects are not supported
• Data compression is not supported
• External storage of objects is not supported
• Some functions for manipulating datasets, dataspaces, and groups have not been implemented
• Some number types, including user-defined number types are not supported. Also number type conversion is limited.

The German Remote Sensing Data Center has generously offered to mirror the HDF ftp server and web page.

The FTP Server location is:

    DLR German Remote Sensing Data Center:
       Host Name:  ftp.dfd.dlr.de
       Location:   software/hdf

The location of the web page is:

    ATMOS User Center at the German Remote Sensing Data Center:
       http://auc.dfd.dlr.de/HDF