Application builders, in contrast, do allow extension by user-written operations and they provide a much greater flexibility in the processing and visualizing the data. The connections between these modules represent the data flow between them. The user can choose from a large set of modules which is supplied by the vendors as a standard set. If it happens that one can not perform an action using these modules, one can write a module oneself or check at an international site if such a module is already written by other users. At these international sites user-written modules from all over the world are gathered and made available to other users.
Prices are also different for the packages.
Most packages are sold at commercial rates. However, DX can currently be bought at a reduced rate for use in scientific areas. Data Visualizer and DX are available at workstations from almost all large workstation vendors, viz. In contrast with these three packages, IRIS Explorer is only available on Silicon Graphics workstations and on CRAY supercomputers. A pleasant side effect of this platform dependency is the fact that the package has been optimized for the available graphical hardware.