It is important to emphasize that Data Explorer is not unique in its capability to create sophisticated visualizations and to be integrated into the formal methodology described in Chapter V. The high-level abstractions can manifest themselves practically in many ways, including other data visualization software. Data Explorer was available and seemed an appropriate test-bed for this research, though it is only one of many products that could fulfill the role defined by the methodology. The end of this section offers a list of several other similar products.

Data Explorer (DX) is an advanced data visualization software package produced by International Business Machines (IBM) which accommodates both developers and end-users of visualizations. Visualizations can be built by creating a visual program in the graphical user interface or by using a scripting language. The end-user can control many aspects of a visualization through the interface, while more advanced users can create new visualizations by adding, removing, or changing modules within the current visual program. DX also allows the creation of new, high-level data-processing or graphical modules.

The DX data model is extremely flexible, though it requires some time to understand and use. It can handle everything from rendering very regular, mesh-connected structures to completely arbitrary sets of polygons. At its heart, the DX data model utilizes sets of positions, connections, and data values associated with one or both of these sets. This simple foundation offers tremendous flexibility in what the model can represent.

In addition, Data Explorer supports a high degree of data and software reusability. Because DX data is self-describing, visual programs retain significant generality and can create a wide class of visualizations. Furthermore, a single DX data file can easily be processed by multiple visual programs. (As will be discussed later, different visualizations are created by altering the trace transformation, the visual program, or both.)

The numerous graphical techniques available in DX can be combined in hundreds of ways, provided that the data satisfies the requirements of the given techniques. DX modules generally do the "right thing" for the data they receive because the data is self-describing. For example, a module which annotates a set of locations with rendered objects whose size and color are dependent on some data value will choose the appropriate graphical technique depending on the dimension of the data (e.g., spheres for scalar values or vector arrows for three-dimensional data).

The Data Explorer software runs on several architectures, including IBM RS/6000, Hewlett-Packard, Silicon Graphics, and Sun workstations. Additional information on Data Explorer can be found in [14] and [24]. Obviously, Data Explorer is not the only general data visualization software available. Some other similar products include AVS by Advanced Visual Systems, Data Visualizer by Wavefront Technologies, IRIS Explorer by Silicon Graphics, and PV-Wave by Visual Numerics. In the public domain, there exists the Geometry Center's Geomview/OOGL and NCSA's Polyview products. Any of these packages could be integrated into the methodology equally as well.