A table provided with D2D lists all depict keys, which are positive integers. Certain depict keys are treated specially. The D2D software will read and render the data in the file on the display. The Export Request Applications that need to know what depictables a forecaster is viewing can use the export request to get a copy of the data used to draw those depictables. If the list is empty, then the forecaster was not viewing any data of the type the application requested.
Applications can use exported data in any way they wish.
For example, consider a hypothetical image processing application that improves contrast in low-light satellite images. When the forecaster starts the application, it can use the export command to request any displayed satellite image and can then read the file that the application interface created and apply its image processing algorithm. The Figure below shows a timing interaction diagram that depicts the transactions between the image processing application and the D2D software. These requests, while available to any application, are really intended just for those applications that are part of the D2D software release. As stated earlier, not only can applications send requests on their standard output, but they can also receive notifications on their standard input.