PG Identifiers

[Comfy.n]

I just found that when I add Project Gutenberg EPUB3 ebooks I don't get their identifier in Calibre, despite them being included as dc:identifier property in content.opf.

However when I add the EPUB format, URI identifier shows up as expected.

Example: https://www.gutenberg.org/ebooks/74324

epub 2 has
<dc:identifier opf:scheme="URI" id="id">http://www.gutenberg.org/74324</dc:identifier>

epub 3 has
<dc:identifier id="id">http://www.gutenberg.org/74324</dc:identifier>

Well I just unpacked the EPUB3, copied that EPUB2 line into the EPUB3's content.opf, and Calibre has set the identifier, so I guess that's something related to the missing opf:scheme="URI" bit.

[kovidgoyal]

They need to use:

<dc:identifier id="id">URN:http://www.gutenberg.org/74324</dc:identifier>

or if they don't want to do that, they they need to create a refines that sets the scheme to URN. Although I would not recommend that, as nothing supports it and the geniuses that created the epub3 spec got their own examples using it wrong in the initial version of the spec. https://idpf.org/epub/301/spec/epub-...ations-errata/

[Comfy.n]

Then I hope they can figure out how to do some mass search and replace like

id="id">http://www.gutenberg.org/{id}</dc:identifier>

with

id="id">URN:http://www.gutenberg.org/{id}</dc:identifier>

... then repack all their EPUB3 files, but for the time being I'm going for epub2.

Thanks for the clarification!