Never delete

From Pelennor

As disk and flash-memory-based storage continues to plummet in cost, we are quickly reaching the point where deleting old or unwanted information offers little or no benefit. In fact, doing so degrades historic integrity -- the ability to reference the temporal semantics of data. Pelennor will indeed allow users to delete or dismiss information they have no interest in, but they will be encouraged to retain everything possible.

Rationale

There are a number of reasons to retain as much data as possible:

• It is common that information considered useful at any given point serves as a foundation for subsequent information. As more information is collected, more context richness and automated compilation of facts becomes possible.
• Historic completeness of data provides useful information in itself, by providing observable trends and progressions. Certain mechanics of Pelennor will leverage this.
• Data mining and artificial intelligence processes may scour old data to learn and bring to surface relevant facts and context which users have long forgotten.

Usefulness

It is a challenge to define the usefulness of data, when determining if it should be disposed of. One plausible assumption is that invalid or deceptive data should be kept out of the system. To the contrary, creating a record of unwanted data is helpful in detecting it in the future. E-mail junk filters commonly use this approach, through Bayesian analysis and other statistical techniques. For example, we may gain the ability to automatically censor or hide content which we feel is inappropriate, distracting, or a waste of time to read. But this filtering will be based entirely upon automatically learned personal preferences, rather than those of filter software designers.