Evaluate Robustness & Longevity

Sure measures of a text's success are the number of people who actually use it, the variety of people who find it useful, and the length of time over which the text is able to engage new readers. All of these measures of success can be evaluated through user profiles—necessary, in any case, for comparing user models to actual users during the design process. Robustness can be improved most effectively by thorough testing among a diverse user group. Longevity is a more subtle matter, as many forgotten artists will attest. Be true to your subject, think (and design) in terms that are important beyond the moment, care for your reader, and keep it simple—all principles advocated elsewhere in this text.