BlueView: virtual document servers for digital libraries

In the BlueView project, digital library services are developed and partially implemented based on the architecture of virtual document servers. Using standard tools like full-text databases or information retrieval systems, object-relational database management systems, and replication and caching services, different heterogeneous local document servers have been integrated into one virtual server. Access to heterogeneous local systems can now be performed via a single query interface, integrating features of database query systems and information retrieval or search services. BlueView distributed query processing allows for combining structured queries against meta data with content-based (text retrieval) queries against full-text collections. Legacy systems such as existing preprint servers, search engines, or meta data (catalog) systems can also be integrated. Meta data and full-text documents can be replicated within this distributed architecture. In particular, in the view of members of a certain university, metadata and documents can be replicated to a local document server and integrated under different local user views. Aspects such as terms and conditions, licenses, diverse versions of documents, different formats, and data structures are considered as well. As application scenarios, preprint servers in Mathematics and the ACM SIGMOD Anthology as local document servers have been integrated into a virtual document server.