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EPUBCheck · Package document (OPF)

EPUBCheck OPF-072: empty Dublin Core element

Updated:

EPUBCheck OPF-072 is a usage message: “Metadata element "…" is empty.” A Dublin Core metadata element in an EPUB 2 package document is empty, and EPUBCheck names it. It is a usage note (shown with -u), but an empty field still gives reading apps nothing to display.

The official message

Metadata element "%1$s" is empty.

Default severity
Usage. Informative only and hidden by default: it appears when EPUBCheck runs with -u (--usage). It does not make the EPUB invalid.
EPUBCheck version
5.4.0

%1$s, %2$s… are filled in with the file, value or element EPUBCheck found.

Typical causes

  • Empty elements such as dc:subject, dc:publisher or dc:description created by a tool without values.
  • Fields exported from a catalogue where the value was blank.
  • A value removed by hand while the element stayed.

How to fix it

  1. Find the element EPUBCheck names.
  2. Fill it with a real value.
  3. Or delete it if you have nothing to put there.

When it's not this

Empty title, identifier or date elements are reported as OPF-055; in EPUB 3 empty metadata is a schema error (RSC-005).

Terms used here

Other OPF messages

  • OPF-073 External identifiers must not appear in the document type declaration.
  • OPF-070 Custom collection role "…" is an invalid URL.
  • OPF-074 Package resource "…" is declared in several manifest items.
  • OPF-067 The resource "…" must not be listed both as a "link" element in the package metadata and as a manifest item.
  • OPF-066 Missing "dc:source" or "source-of" pagination metadata. The pagination source must be identified using the "dc:source" and "source-of" properties when the content includes page break markers.
  • OPF-065 Invalid metadata declaration, probably due to a cycle in "refines" metadata.

Sources

Message text and severity from EPUBCheck 5.4.0 (W3C, BSD-3-Clause). Explanation by EpubCC.

FAQ

What does EPUBCheck OPF-072 mean?

EPUBCheck OPF-072 is a usage message: “Metadata element "…" is empty.” A Dublin Core metadata element in an EPUB 2 package document is empty, and EPUBCheck names it. It is a usage note (shown with -u), but an empty field still gives reading apps nothing to display.

Is OPF-072 an error?

OPF-072 is reported as usage by default. Informative only and hidden by default: it appears when EPUBCheck runs with -u (--usage). It does not make the EPUB invalid.