Preservation of digital libraries is a complicated process that must begin with an appraisal of what is to be preserved before it moves on to the question of how to best preserve it. In order to fully understand the nature and attributes of digital documents and digital libraries, it is necessary to place them in the context of some of the other types of cultural artifacts that have been preserved over time, and to look at how the issues of fixity (stability) and durability (longevity) of these other artifacts have been addressed. Cultural artifacts are products of the “processing” of “parts” into “products” of varying fixity and durability. Efforts to define digital documents and digital libraries are at the root of current research into the best ways of preserving both, and have been deeply affected by the blurred boundaries between parts, processes, and products; by the continually changing nature of digital entities; and by the entities' low fixity and low durability. Current research projects into the preservation of digital entities have concluded that a necessary first step is the appraisal of the “significant properties” of digital objects. Now is the time for the creation of a range of digital-derivative products of high fixity and high durability that each effectively captures some significant property of the original “digital performance” or “digital organism.”