A digital library enables users to interact effectively with informati
on distributed across a network. These network information systems sup
port search and display of items from organized collections. In the hi
storical evolution of digital libraries, the mechanisms for retrieval
of scientific literature have been particularly important. Grand visio
ns in 1960 led first to the development of text search, from bibliogra
phic databases to full-text retrieval. Next, research prototypes catal
yzed the rise of document search, from multimedia browsing across loca
l-area networks to distributed search on the Internet. By 2010, the vi
sions will be realized, with concept search enabling semantic retrieva
l across large collections.