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<fieldset><h1>Phase Out JHV</h1></fieldset>

<h2>
The need to phase out JHV</h2>

Viewing HDF files visually on different platforms is always a challenge.
With the Java<sup><font size=-2>TM</font></sup> technology, the HDF Java
team was able to develop HDF visualization tools such as the Java HDF
Viewer (JHV) and the HDF5 View (H5View). Using the JHV, users can browse
through the hierarchical structure of HDF4 files and view content of HDF4
objects. The H5View is a Java-based tool for browsing and editing HDF5
files. With the H5View, users can easily create and delete HDF5 objects,
and modify the content of HDF5 objects and attributes. However, there is
variety of challenging problems in visualizing HDF files.
<p> The JHV and H5View support only a single format, HDF4 or HDF5 files,
       respectively. Since HDF4 and HDF5 files are incompatible, JHV cannot
       read HDF5 files, and vice versa. To be able to read both HDF4 and HDF5
       files, users have to install both tools. If both HDF4 and HDF5 files
       are named with the same extension "hdf", users have no way to know
       which tool to use in advance.<p> The JHV and H5View require different Java Virtual Machine. The JHV
       was built and can only run at JDK1.1.x. It does not work on Java 2
       platform(JDK 1.2.x or JDK 1.3.x). The H5View was developed at Java 2
       and does not run on JDK 1.1.x or earlier version of Java virtual machines.
       To build the JHV and H5View from the source or install the pre-built
       binary bundles without JRE, users have to install both JDK1.1.x and
       Java 2 in their machine.<p> Supporting both the JHV and H5View are expensive. The HDF support group
       and HDF Java team have to maintain separate bug and feature-request lists
       and web pages for the JHV and H5View. The tool developers have to work
       for both the JHV and H5View projects, which include source tree, building
       environment/scripts, documentation and release work.<p> Converting data objects between HDF4 and HDF5 is not supported with the
       JHV or H5View. Since both the JHV and H5View only support a single format,
       and opens only one file a time, users cannot copy/move objects of different
       types (HDF4 or HDF5) between files.


<p>
The new tool, NCSA HDF Viewer (HDFView), is a visual tool for browsing and editing
NCSA HDF4 and HDF5 files. The HDFView will be implemented by using Java 2 Platform
that is designed to be machine-independent. The interface and features of the
HDFView are the same for all platforms. When the user opens an HDF file, the
HDFView will call the HDF4 or the HDF5 library based on the file type and displays
the structure of the file in a tree with data groups and data objects represented
as conventional folders and icons. Users can easily expand or collapse folders to
navigate the hierarchical structure of the file.

<p>
HDFView is the tool to substitute the JHV as the JHV to be phased out. As editing
features are added to its future release, HDFView will also be the tool to phase
out the H5View.

<h2>
The difference between JHV and HDFView</h2>
Although HDFView is the tool to substitute JHV, the Java virtual machine, the GUI
interface and object model are different. The following table is a list of
differences between the two tools.

<p>
<center>
<table border>

<tr>
<td></td>
<td><b>JHV</b></td>
<td><b>HDFView</b></td>
</tr>

<tr>
<td>Java Virtual Machine</td>
<td>JDK/JRE 1.1.x</td>
<td>JDK/JRE 1.3.x</td>
</tr>

<tr>
<td>HDF Object Model</td>
<td>Designed only for HDF4</td>
<td>Common model for HDF4/5</td>
</tr>

<tr>
<td>Implementing GUI interface</td>
<td>java.awt classes, interface for HDF4 only</td>
<td>javax.swing classes, common interface for HDF4/5</td>
</tr>

<tr>
<td>Supporting file format</td>
<td>HDF4 and HAIF ASCII</td>
<td>HDF4 and HDF5</td>
</tr>

<tr>
<td>Multiple file access</td>
<td>No</td>
<td>Yes </td>
</tr>

<tr>
<td>Mouse-drag to select 2D subset</td>
<td>Yes</td>
<td>No</td>
</tr>

<tr>
<td>Animations for SDS or raster images</td>
<td>Yes</td>
<td>No</td>
</tr>

<tr>
<td>Image contrast, smooth, and contour</td>
<td>Yes</td>
<td>No</td>
</tr>

<tr>
<td>Make transparent and overlays images</td>
<td>Yes</td>
<td>No</td>
</tr>

<tr>
<td>Field selection in Vdata</td>
<td>Yes</td>
<td>No</td>
</tr>

<tr>
<td>User preference</td>
<td>Yes</td>
<td>No</td>
</tr>

<tr>
<td></td>
<td>Yes</td>
<td>No</td>
</tr>

</table>
</center>

<h2>
For further information</h2>

General information about HDF and HDF4 and HDF5 are available at:
<br><a href=""></a>

<p>
Information about the HDFView tool and related products is available
at:
<br><a href="/hdf-java-html/index.html">
/hdf-java-html/</a>


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