Awareness services for digital libraries

We propose an architecture for Digital Library repositories where one or more data stores persistently hold the digital objects (e.g., documents), and interact with clients that perform indexing, replication, intellectual property management, revenue management, and other functions. One of the most critical components in such stores is the awareness mechanism, used to notify clients of inserted, deleted or changed objects. In this paper we survey the various awareness schemes (including snapshot, timestamp and log based), describing them all as variations of a single unified scheme. This makes it possible to understand their relative differences and strengths. In particular we focus on a signature-based awareness scheme that we believe is especially well suited for digital libraries, and show enhancements to improve its performance.