W3C RDF infrastructure

algae - graph query library run over various RDF data stores.

ACLs system - performs access control and administration for W3C website.
Good use of SQL -> RDF mapping.
efficient at large scale - manages access for 7000 users and 6500 IP addrs to over 200,000 URIs.

annotea - web page annotation system
implemented mostly as a wrapper for algae queries
experiment in efficiency of semi-centralized data stores.