EpubCCEPUBCheck OPF-028: prefix used but undeclared
Updated:
EPUBCheck OPF-028 is an error message: “Undeclared prefix: "…".” A property uses a prefix that is not declared in the package document's prefix attribute. Apart from the reserved prefixes, every prefix must be mapped to a vocabulary URI before it can be used.
The official message
Undeclared prefix: "%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
- Vendor properties such as ibooks:version used without declaring the ibooks prefix.
- The prefix attribute was removed or cleaned up while properties still use it.
- A typo in the prefix of a property, so it no longer matches the declared one.
How to fix it
- Read the prefix EPUBCheck names.
- Add its mapping to the prefix attribute of the package element. Write each mapping as the prefix name, a colon, one space and the vocabulary URI, and separate mappings with whitespace, for example
prefix="ibooks: http://vocabulary.itunes.apple.com/rdf/ibooks/vocabulary-extensions-1.0/ foaf: http://xmlns.com/foaf/spec/". - Or, if the property is not needed, remove it.
When it's not this
If the prefix is declared but the declaration is badly written, that is a variant of OPF-004.
Terms used here
Other OPF messages
OPF-027Undefined property: "…".OPF-029The file "…" does not appear to match the media type …, as specified in the OPF file.OPF-026Found malformed property value: "…".OPF-030The unique-identifier "…" was not found.OPF-025Property value list "…" is not allowed, only one value must be specified.OPF-031File 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.