  Although recording of usage data is common in scholarly information services,
its exploitation for the creation of value-added services remains limited due
to concerns regarding, among others, user privacy, data validity, and the lack
of accepted standards for the representation, sharing and aggregation of usage
data. This paper presents a technical, standards-based architecture for sharing
usage information, which we have designed and implemented. In this
architecture, OpenURL-compliant linking servers aggregate usage information of
a specific user community as it navigates the distributed information
environment that it has access to. This usage information is made OAI-PMH
harvestable so that usage information exposed by many linking servers can be
aggregated to facilitate the creation of value-added services with a reach
beyond that of a single community or a single information service. This paper
also discusses issues that were encountered when implementing the proposed
approach, and it presents preliminary results obtained from analyzing a usage
data set containing about 3,500,000 requests aggregated by a federation of
linking servers at the California State University system over a 20 month
period.
