Using distributed objects for digital library interoperability

Information repositories are just one of many services tomorrow's digital libraries might offer. Other services include automated news summarization, trend analysis across news repositories, and copyright-related facilities. This distributed collection of services has the potential to be enormously helpful in performing information-intensive tasks. It could also turn such tasks into confusing, frustrating annoyances by forcing programmers and users to learn many interfaces and by confronting users with the bewildering details of fee-based services that were previously only accessible to professional librarians. The Stanford Digital Library project is addressing the problem of interoperability, which is particularly important because standardization efforts are lagging behind the development of digital library services. The authors used CORBA to implement information-access and payment protocols. These protocols provide the interface uniformity necessary for interoperability, while leaving implementers a large amount of leeway to optimize performance and to provide choices in service performance profiles. The authors' initial experience indicates that a distributed object framework-and its access protocol in particular-do give clients and servers the flexibility to manage their communication and processing resources effectively.