(WAIS, Fulcrum)
Z39.50 is a national standard defining a protocol for computer-to-computer information retrieval. Z39.50 makes it possible for a user in one system to search and retrieve information from other computer systems (that have also implemented Z39.50) without knowing the search syntax that is used by those other systems. Z39.50 is an American National Standard that was originally approved by the National Information Standards Organization (NISO) in 1988.
See http://lcweb.loc.gov/z3950/