Harp: A distributed query system for legacy public libraries and structured data bases

The main purpose of a digital library is to facilitate users easy access to enormous amount of globally networked information. Typically, this informa tion includes preexisting public library catalog data, digitized document c ollections, and other databases. In this article, we describe the distribut ed query system of a digital library prototype system known as HARP. In the HARP project, we have designed and implemented a distributed query process or and its query front-end to support integrated queries to preexisting pub lic library catalogs and structured databases. This article describes our e xperiences in the design of an extended Sequel (SQL) query language known a s HarpSQL. It also presents the design and implementation of the distribute d query system. Our experience in distributed query processor and user inte rface design and development will be highlighted. We believe that our proto typing effort will provide useful lessons to the development of a complete digital library infrastructure.