This column presents a continuation of an article published in last month's issue of "Libraries in Computers," in which the author began to consider what it might mean to build dynamic, instantaneous libraries based solely on the materials held on the computers of people in the same space. The goal of this column is to think about what libraries in computers need to look like for them to serve as well as libraries we already know. In order to build a physical library, certain well-known steps would be followed: assess the needs; call for proposals; review bids by architectural firms; pick one, then work with a selected firm to design a space that meets the needs. A similar process is followed when designing software, where diagrams of boxes and arrows, mocked-up screen shots, cost estimates, and a timetable are comparable in function to blueprints for real buildings. Any good set of blueprints should give you a feel for how people will move in, out, between, and around the physical space of a library to get from one section to another. But even that does not necessarily speak to the cognitive wayfinding that library users perform. The best libraries are designed to support the process of finding, studying, questioning, and recombining information. These days we can accomplish many of the same tasks with a click through Wikipedia here, a quick look-up at Amazon.com there, and a link to a map server in between. Maybe doing so is qualitatively different from running around back and forth in the physical library to find the same answers to the same questions. Maybe the physical movement and its cognitive affiliation with what you learn and where you learn it builds a stronger mental connection, one that's more likely to "stick" over time. What matters, then, in our mental blueprints for libraries in computers, is not just the availability of diverse resources, nor even the ability to connect and combine those resources. When designing software, or a building, the author suggests, one of the first things to account for is which elements will tend to change over time, and how often they will change. In this case we are assessing needs for libraries in computers--dynamic, instantaneous libraries that exist only in our computers and the computers nearby. A central element of our blueprints will just have to be "lots of other computers and the resources they contain coming and going all the time." In this article, the author indicates he has long thought of libraries as storehouses of great works, rare materials, and a lot of common stuff that comes and goes often. He concludes that maybe we have always had some pulsing content, but to build libraries from scratch today, it might help to recognize that all we have is pulsing content.