7 Conclusions

The design and implementation of the ADS bibliographic services has been driven by the desire to provide flexible search capabilities to the astronomical community. The original decision to create our own suite of software tools for indexing and searching the databases has proven to be an important one as it has given us the freedom to continuously enhance and tailor the software to our users' needs. With freedom, however, also came the responsibility of maintaining a complex system which has now been ported to a variety of hardware and software platforms. Fortunately, the adoption of standard programming languages and coding techniques has greatly facilitated the task.

Over the years, the ADS has evolved from being a user-oriented system to becoming an open service for the discovery and retrieval of bibliographic data, allowing integration of our capabilities in the operation of other information providers. At the same time, our system was expanded from being simply a searchable archive of bibliographic references to being a service offering relational links among records within our system and to resources available elsewhere. In this respect, the design of a hierarchical framework for the management of bibliographic resources has provided the required level of flexibility and extensibility. With the recent proliferation of mirror sites for popular resources in astronomy, we have adopted a simple yet powerful mechanism for the resolution of links to resources available at multiple locations, adding user customization to the resolution process.

With the completion of full-text coverage of the astronomical literature over the next few years, the ADS will be able to significantly increase the holdings of its citation database and provide full-text search and retrieval capabilities. With the adoption of new technologies and standards in electronic data interchange, the ADS is likely continue to play an important role in the integration of network services in astronomy.

Acknowledgements

The usefulness of a bibliographic service is only as good as the quality and quantity of the data it contains. The ADS project has been lucky in benefitting from the skills and dedication of several people who have significantly contributed to the creation and management of the underlying datasets. In particular, we would like to acknowledge the work of Elizabeth Bohlen, Donna Thompson, Markus Demleitner, and Joyce Watson.

Funding for this project has been provided by NASA under grant NCC5-189.