Second order relational operators are functions which take lists which have been generated by a database query, and from those lists form sets of other lists, which can then be merged and sorted on the basis of one or more of the attributes of the items in the lists. The NASA Astrophysics Data System is unique among bibliometric information retrieval systems in the degree to which users are permitted to make use of these concepts.
Given a knowledge of how the second order operators work, ADS users can create complex logical algebras which facilitate the discovery of very highly specific information.
The Astrophysics Data System (ADS) is the search system of choice for
Astronomers world-wide. The searchable database contains over 2.6
million bibliographic records. In addition the ADS has over 2 million
scanned article pages from about 280,000 articles, dating back as far
as 1829. There are currently more than 10,000 regular users (more
than 10 queries/month). ADS users issue almost 1 million queries per
month and receive 40 million records and 1.2 million scanned article
pages per month. One important aspect of the ADS is the system of
links to other data providers. We have currently more than 3 million
links to other on-line resources. The ADS is accessed from almost 100
countries with a wide range of the number of queries per country. In
order to improve access from different parts of the world, we maintain 9 mirror sites of the ADS in Brazil, Chile, China, England, France, Germany, India, Japan, and Russia. Automatic procedures facilitate keeping these mirror sites up-to-date over the network. The ADS is funded by NASA Grant NCC5-189. The ADS is available at:
http://ads.harvard.edu
KEYWORDS: Advanced distributed simulations, Astronomy, Data archive systems, Field emission displays, Cadmium sulfide, Observatories, Data centers, Databases, Astrophysics, Information technology
The AVO has the potential to significantly change and improve the way astronomers can utilize data and conduct their research. In order to make this happen, the most important challenge of the AVO will be to enable astronomers to find what they need for their research. This will be more and more difficult the more data are included in the AVO. We believe that there already exists a search system that can be used as the basis for this search capability of the AVO. Properly utilized this basis will allow the AVO to much more quickly reach its goals.
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