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Glossary

What is Dublin Core metadata (dc:*)?

Updated:

EPUB metadata uses Dublin Core elements in the package document: dc:identifier, dc:title and dc:language are required, and dc:creator, dc:date, dc:publisher and others are optional. EPUB 3 also requires a dcterms:modified timestamp.

Why it matters when you convert a PDF to EPUB

A PDF often has a useless internal title (a file name like "Microsoft Word - draft3.docx") or none. A converter has to choose a real title, detect the language of the text for dc:language (which drives hyphenation and text-to-speech) and generate a stable unique identifier.

Related terms

EPUBCheck messages about this

  • OPF-030 The unique-identifier "…" was not found.
  • OPF-053 Date value "…" does not follow recommended syntax as per http://www.w3.org/TR/NOTE-datetime:….
  • OPF-085 "dc:identifier" value "…" is marked as a UUID, but is an invalid UUID.
  • OPF-092 Language tag "…" is not well-formed: …
  • OPF-048 Package tag is missing its required unique-identifier attribute and value.
  • OPF-054 Date value "…" is not valid as per http://www.w3.org/TR/NOTE-datetime:….
  • OPF-065 Invalid metadata declaration, probably due to a cycle in "refines" metadata.
  • NCX-001 NCX identifier ("…") does not match OPF identifier ("…").

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FAQ

What is Dublin Core metadata (dc:*)?

EPUB metadata uses Dublin Core elements in the package document: dc:identifier, dc:title and dc:language are required, and dc:creator, dc:date, dc:publisher and others are optional. EPUB 3 also requires a dcterms:modified timestamp.