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By far the most flexible approach with all-around utility appears to be exposing unAPI in Fedora. One
DSpace Integration
As a proof of concept, I also implemented an OAI-PMH resolver, designed to provide unAPI services for any application that exposes OAI-PMH. As DSpace provides OAI-PMH services, providing Zotero support only involved the additional steps of enabling the MODS crosswalk and adding the unAPI microformat identifier and unAPI service link to display-item.jsp.
Although the OAI-PMH resolver would also work with Fedora's OAI provider, the Fedora resolver allows for more flexibility. The Fedora resolver is not limited to the formats exposed by OAI. If Zotero integration is the only use case, this additional flexibility isn't important. It shouldn't be difficult to write a DSpace-specific resolver as well. I'm just not familiar enough with DSpace's API to do it myself.