  The NSDL (National Science Digital Library) is funded by the National Science
Foundation to advance science and match education. The inital product was a
metadata-based digital library providing search and access to distributed
resources. Our recent work recognizes the importance of context - relations,
metadata, annotations - for the pedagogical value of a digital library. This
new architecture uses Fedora, a tool for representing complex content, data,
metadata, web-based services, and semantic relationships, as the basis of an
information network overlay (INO). The INO provides an extensible knowl-edge
base for an expanding suite of digital library services.
