Information dissemination is a powerful mechanism for finding
information in wide-area environments. An information dissemination
server accepts long-term user queries, collects new documents from
information sources, matches the documents against the queries, and
continuously updates the users with relevant information.
                                   
This paper is a retrospective of the Stanford Information Filtering
Service (SIFT), a system that as of April 1996 was processing over
40,000 worldwide subscriptions and over 80,000 daily documents.  The
paper describes some of the indexing mechanisms that were developed
for SIFT, as well as the evaluations that were conducted to select a
scheme to implement.  It also describes the implementation of SIFT,
and experimental results for the actual system.  Finally, it also
discusses and experimentally evaluates techniques for distributing a
service such as SIFT for added performance and availability.