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Open eBook and Dublin Core
Open eBook (or OEB), or formally, the Open eBook Publication Structure (OEBPS), is a legacy e-book format "based primarily on technology developed by SoftBook Press"[2] and on XML; it has been superseded by the EPUB electronic publication standard.
Open eBook is a ZIP file plus a Manifest file. Inside the package a defined subset of XHTML may be used, along with CSS and Dublin Core metadata. The default file extension is .opf (OEB Package Format).
While I haven't absolutely confirmed this, my understanding is that DC support carried over into EPUB.