Evaluating Emulation and Migration: Birds of a Feather?

Evaluating the results of a digital preservation action, be it migration or emulation, is a complex task. The usual approach for migration is to evaluate object properties after the migration. For emulation strategies the result of the rendering of the object is evaluated. In this paper we argue that the change of object properties when migrating is not sufficient evidence if a digital preservation action is successful or not. Even for migration the rendering process of the digital object is crucial, and as such evaluating object properties is not enough. The difference in evaluation between emulation and migration as a strategy for digital preservation becomes blurred as migration results have to be compared based on the rendering of the target format and the environment used to render the migrated digital object. Evaluation of object properties when migrating will only validate a necessary condition for preserving significant properties, i.e. whether the information underlying a specific property is still present in an object after migration. It cannot guarantee that the rendering based upon the migrated object will exhibit a specific significant property. In this paper we show the view-path of digital objects and explain how emulation and migration actions affect it. We then compare the changes that occur in the view-path and show that these are at least as severe when migrating a digital object as when emulating its rendering environment.