After the examination is complete, the data is recorded on an archive media. In Tacoma, a CDROM of the ExamFolder data is created and the location of the data is recorded in the database for subsequent retrieval. Each examination at the Tacoma testbed consists of about 20 megabytes(Mbytes) of data. In addition to archiving the actual data, a lossy compression which eliminates image details is done to reduce the folder to .1 MByte. The compressed ExamFolder data is kept online. At current disk prices, it costs about 10¢ in disk hardware to keep each compressed folder online.

Reviewing Historical Data

Obviously the online information has historical interest. For example:

• Cargo is found in variance with the manifest. The analyst would revisit all previously inspected cargoes from the same consignee and shipper.
• A container or vehicle is found with a false compartment. Every prior inspection of that same container or vehicle would be reviewed to determine when the false compartment first appeared.
• Similar cargo loads can be retrieved for comparison

To review historical data, another computer program is provided, see Figure 6. Based on selection criteria provided by the Analyst, the program displays thumbnails of each matching image.