To enable information to be usable the consumer must be presented with the following:

• A set of readable bytes. These must contain the information that was saved, but do not need to be the exact same bytes that were saved.
• An application that can read these bytes. This needs to be accessible to and usable by today’s users.
• An operating system that can run this application.
• Some hardware on which the operating system runs.

Aligning this stack can be very difficult as all of the elements are constantly changing – new hardware is released, operating systems are upgraded and applications change. Take for example project plans held in Microsoft Project 4.0. Despite being only 10 years old these can no longer be read by the current MS Project versions and the versions of Project that can read them will not run under Windows Vista or XP. This data has effectively been lost.