The NASA Astrophysics Data System: The search engine and its user interface

The ADS Abstract and Article Services pros ide access to the astronomical l iterature through the World Wide Web (WWW). The forms based user interface provides access to sophisticated searching capabilities that allow our user s to find references in the fields of Astronomy, Physics/Geophysics, and as tronomical Instrumentation and Engineering. The returned information includ es links to other an-line information sources, creating an extensive astron omical digital library. Otter interfaces to the ADS databases provide direc t access to the ADS data to allow developers of other data systems to integ rate our data into their system. The search engine is a custom-built software system that is specifically ta ilored to search astronomical references. It includes an extensive synonym list that contains discipline specific knowledge about search term equivale nces. Search request logs show the usage pattern of the various search system cap abilities. Access logs show the world-wide distribution of ADS users. The ADS can be accessed at: http://adswww.harvard.edu.