The shift from traditional libraries to the digital is not merely atechnological evolution, but requires a change in the paradigm by which peopleaccess and interact with information.
A traditional library is characterized by the following:
By contrast, a digital library differs from the above in the followingways:
The total number of different books produced since printing began does notexceed one billion. (The number of books now published annually is less thanone million.) If an average book occupies 500 pages at 2,000 characters perpage, then even without compression it can be stored comfortably in onemegabyte. Therefore, one billion megabytes are sufficient to store all books.This is 1015 bytes, or one petabyte. At commercial prices of $20 pergigabyte, this amount of disk storage capacity could be purchased for $20million. So it is certainly feasible to consider storing all booksdigitally.
A database of a billion objects, each of which occupies one megabyte, islarge but not inconceivable. Once one is comfortable with sizes of this kind,it is feasible to imagine a thousand such databases, or to envision them all asportions of the same global collection. This amount of storage is sufficient tohouse not only all books, but all of the following:
When information is digitized and accessible over a network, it makes littlesense to speak of its "location," although it is technically resident on atleast one storage device somewhere, and that device is connected to at leastone computer. If the information is available at multiple mirror sites, it iseven less meaningful to speak of it being in a "place." While traditionallibraries measure their size by number of books, periodicals and other itemsheld, the relevant statistic for a digital library is the size of the corpusits users may access. This means that digital libraries will want to expandtheir "holdings" by sharing digital links with other libraries. Unfortunately,there seems to be very little sharing of this sort taking place at present.
How can we understand the unwillingness of libraries to share content? Thequestion goes back to the old measure of the size of a traditional library¾thenumber of books it holds. When a library expends funds to assemble digitizedworks, it loses a portion of its prestige (or thinks it does) by allowing otherlibraries to copy or access its data. Ultimately, however, all materialshould be accessible from every library.
In 1998, Vice President Gore stated that "A new wave of technologicalinnovation is allowing us to capture, store, process and display anunprecedented amount of information about our planet and a wide variety ofenvironmental and cultural phenomena. ... I believe we need a 'Digital Earth.'A multi-resolution, three-dimensional representation of the planet, into whichwe can embed vast quantities of geo-referenced data" (Gore 1998). He thencalled on scientists to create a digital map of the earth at a resolution ofone meter. Such a project will require technical innovation beyond thatrequired even for a digital library containing every book ever written. Thearea of the earth in square meters is about 5 x 1014. Storing twomegabytes of data per square meter (which would include terrain data, imaging,environmental and other pertinent information) will require 1018bytes, an amount roughly equal to the amount of digital storage currentlypresent on earth.