The many challenges to maintaining stored information and ways to overcome them. Raymond Blum with Betsy Beyer, acmque – February 6, 2019 Volume 16, issue 6 – “Digital permanence has become a prevalent issue in society. This article focuses on the forces behind it and some of the techniques to achieve a desired state in which “what you read is what was written.” While techniques that can be imposed as layers above basic data stores—blockchains, for example—are valid approaches to achieving a system’s information assurance guarantees, this article won’t discuss them. First, let’s define digital permanence and the more basic concept of data integrity.

Data integrity is the maintenance of the accuracy and consistency of stored information. Accuracy means that the data is stored as the set of values that were intended. Consistency means that these stored values remain the same over time—they do not unintentionally waver or morph as time passes. Digital permanence refers to the techniques used to anticipate and then meet the expected lifetime of data stored in digital media. Digital permanence not only considers data integrity, but also targets guarantees of relevance and accessibility: the ability to recall stored data and to recall it with predicted latency and at a rate acceptable to the applications that require that information. To illustrate the aspects of relevance and accessibility, consider two counterexamples: journals that were safely stored redundantly on Zip drives or punch cards may as well not exist if the hardware required to read the media into a current computing system isn’t available. Nor is it very useful to have receipts and ledgers stored on a tape medium that will take eight days to read in when you need the information for an audit on Thursday…”