epubcheck 5.1.0 failing on books with TDM opt-outs

[liisamk]

When we test including a TDM opt-out in our OPF files, we are consistently getting an epubcheck error: ERROR (OPF-028): Undeclared prefix: "tdm"

Since this is an industry standard that many publishers around the world are starting to implement, it should be fixed.

Example file TK

[TzviyaSiegman]

for context https://www.w3.org/community/reports/tdmrep/CG-FINAL-tdmrep-20240510/#sec-epub3

[mattgarrish]

Have you declared a prefix as in the example @TzviyaSiegman cited?

If so, what version of epubcheck are you running? I can't reproduce the error if the prefix is declared.

If you're wanting to skip declaring a prefix, you need to get the epub standard amended to add tdm as a reserved prefix.

[liisamk]

Ah- mea culpa. The prefix was not declared. When we add it, the validation in 5.1.0 works.