The NASA Astrophysics Data System: Architecture

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 fielded data and metadata, while discipline-specific knowledge is segregated in a set of files independent of the bibliographic data itself. This ancillary information is used by the database management software to compile field-specific index files used by the ADS search engine to resolve 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 resolution of links available from different locations has been generalized to allow its control through a site- and user-specific preference database. To improve global access to the ADS data holdings, a number of mirror sites have been created by cloning the database contents and software on a variety of hardware and software platforms. The procedures used to create and manage the database and its mirrors have been written as a set of scripts that can be run in either an interactive or unsupervised fashion. The modular approach we followed in software development has allowed a high degree of freedom in prototyping and customization, making our system rich of features and yet simple enough to be easily modified on a day-to-day basis. We conclude discussing the impact that new datasets, technologies and collaborations is expected to have on the ADS and its possible role in an integrated environment of networked resources in astronomy. The ADS can be accessed at: http://adswww.harvard.edu