Jerome P. McDonough has made "Aligning METS with the OAI-ORE Data Model" available in IDEALS.
Here's an excerpt:
(OAI-ORE) specifications provide a flexible set of mechanisms for transferring complex data objects between different systems. In order to serve as an exchange syntax, OAI-ORE must be able to support the import of information from localized data structures serving various communities of practice. In this paper, we examine the Metadata Encoding & Transmission Standard (METS) and the issues that arise when trying to map from a localized structural metadata schema into the OAI-ORE data model and serialization syntaxes.