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Pulling all of these considerations together, the simplest approach to the "book" scenario would likely be to create all resources without user-provided identifiers. The "book" would be a container and the pages, thumbnail, and METS files would all be binaries. Relationships between the resources would be established (#hasPage, #nextPage, #isThumbNailOf, etc). To facilitate more robust search, the metadata packed into the METS file could be extracted out into properties. Likewise, using property terms that are defined in commonly used, linked data vocabularies will aid in cross-repository, cross-institutional normalization.