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EPUBCheck · Package document (OPF)

EPUBCheck OPF-027: property not in vocabulary

Updated:

EPUBCheck OPF-027 is an error message: “Undefined property: "…".” A property is not defined in the vocabulary it belongs to, so reading apps will not understand it. EPUBCheck knows the EPUB vocabularies and checks every unprefixed or reserved-prefix property against them.

The official message

Undefined property: "%1$s".

Default severity
Error. The EPUB breaks a rule of the specification and is invalid. Stores and Send to Kindle may reject it, and EPUBCheck exits with status 1.
EPUBCheck version
5.4.0

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

Typical causes

  • A misspelling, such as properties="cover" instead of "cover-image".
  • An invented property name used for a tool's own purposes.
  • A property from a newer or older version of a vocabulary that EPUBCheck does not recognise.

How to fix it

  1. Read the property EPUBCheck quotes.
  2. Look it up in the EPUB 3.3 vocabularies and correct the spelling if it exists.
  3. If it is a custom property, put it under your own prefix declared in the prefix attribute, or remove it.

When it's not this

If the property uses a prefix that is not declared, EPUBCheck reports OPF-028 instead.

Terms used here

Other OPF messages

  • OPF-026 Found malformed property value: "…".
  • OPF-028 Undeclared prefix: "…".
  • OPF-025 Property value list "…" is not allowed, only one value must be specified.
  • OPF-029 The file "…" does not appear to match the media type …, as specified in the OPF file.
  • OPF-030 The unique-identifier "…" was not found.
  • OPF-031 File listed in reference element in guide was not declared in OPF manifest: ….

Sources

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

FAQ

What does EPUBCheck OPF-027 mean?

EPUBCheck OPF-027 is an error message: “Undefined property: "…".” A property is not defined in the vocabulary it belongs to, so reading apps will not understand it. EPUBCheck knows the EPUB vocabularies and checks every unprefixed or reserved-prefix property against them.

Is OPF-027 an error?

OPF-027 is reported as error by default. The EPUB breaks a rule of the specification and is invalid. Stores and Send to Kindle may reject it, and EPUBCheck exits with status 1.