The NASA Astrophysics Data System: Architecture,'' A&AS, 143, 85 Adobe, Inc Adobe Acrobat Reader, http://www.adobe.com/prodindex/acrobat/alternate.html Adobe Postscript 1990 Adobe Systems 1990, ``Postscript Language Reference Manual, Second Edition

Abstract. The powerful discovery capabilities available in the ADS bibliographic services are possible thanks to the design of a flexible search and retrieval system based on a relational database model. Bibliographic records are stored as a corpus of structured documents containing elded data and metadata, while discipline-specic knowl-edge is segregated in a set of les independent of the bib-liographic data itself. This ancillary information is used by the database management software to compile eld-speci c index les used by the ADS search engine to re-solve user queries into lists of relevant documents. The creation and management of links to both internal and external resources associated with each bibliography in the database is made possible by representing them as a set of document properties and their attributes. The res