Provenance software promises to track down digital info's secrets — in the name of trust
A large blue diagram fills the computer monitor in James Frew’s office at the University of California, Santa Barbara; it’s a graphical representation of the life history of data used to create a map of ocean color around the world. Several tightly spaced vertical lines run down the left side of the screen, illustrating the flow of information toward the end product. As he scrolls down, small boxes containing data source labels come into view on the right side. Horizontal lines lead from the boxes to the vertical lines on the left, mapping how each boxed element, or data source, feeds into the main flow.
“In a sense, what I’m doing is pointing to this ocean-color result and saying, ‘Where’d it come from?’” explains the professor of geoinformatics. “This prototype system is designed to apply a set of rules to the provenance so that it goes all the way back to the start. And at each point it asks, ‘Is this good?’”
Frew tracks down through the boxes, evaluating each as he goes: “In this case it’s good because the file name happens to match a pattern we trust, and the file hasn’t been modified since it was put there. This one lives in a standard place and is part of the operating system, so I trust it. I trust this next one transitively because it was created with verified data and a verified process. And I trust this because it’s under the control of a revision system, and whoever created the program hasn’t modified it since, so I trust it because I trust that control system.”
Finally, using his index finger to draw a circle in the air around all the boxes on the right side, he says, “Because I trust all this stuff, I trust the ocean color that came from it. We have the provenance and then we go back through it and apply automatic rules to decide, the idea being that if we trust all the antecedents, we will trust, by derivation, the end result. That’s provenance at work.”
Provenance is an old concept, useful in examining valuable objects like fine wine or old books. In the art world, for instance, it refers to the past of a painting, a sculpture or other object — that is, the chain of ownership used mainly to determine authenticity.