Digital libraries, like physical libraries, are not about the technology that supports them (although they would be useless without it), and they are not about metadata standards yet to be developed, although without records and pointers, digital libraries would suffer the maladies of full-text searching pointed out by Blair and Maron.3 Digital libraries are not about data structures and electronic representations. Digital libraries are not about the interfaces that make their use more or less effective. It is even possible to suggest that digital libraries are not about users, because users, conceived as a set of individuals, are notoriously idiosyncratic in behavior, and, therefore, remain a daunting variable in the information system design equation. Digital libraries, like physical libraries, are about communities: the interests, behaviors, goals, and recognizable traits that belong to groups of people. However, unlike their ‘‘traditional’’ cousins, digital libraries already are serving communities in ways not possible in traditional libraries. It is almost certain that digital libraries will serve communities in ways not yet imagined.