  In recent years, a variety of digital repository and archival systems have
been developed and adopted. All of these systems aim at hosting a variety of
compound digital assets and at providing tools for storing, managing and
accessing those assets. This paper will focus on the definition of common and
standardized access interfaces that could be deployed across such diverse
digital respository and archival systems. The proposed interfaces are based on
the two formal specifications that have recently emerged from the Digital
Library community: The Open Archive Initiative Protocol for Metadata Harvesting
(OAI-PMH) and the NISO OpenURL Framework for Context-Sensitive Services
(OpenURL Standard). As will be described, the former allows for the retrieval
of batches of XML-based representations of digital assets, while the latter
facilitates the retrieval of disseminations of a specific digital asset or of
one or more of its constituents. The core properties of the proposed interfaces
are explained in terms of the Reference Model for an Open Archival Information
System (OAIS).
