Metadata Source Plugin, advice needed

[Boilerplate4U]

I also found some more non ISBN as well but most without the schema attribute. Since the attribute it optional it's possible to utilize pattern matching testing to identify the different types as they differ quite a lot:

ISBN
<dc:identifier opf:scheme="isbn">9780000000001</dc:identifier>

JDCN
<dc:identifier opf:scheme="jdcn">915869090000000000DD</dc:identifier>

UUID (GUID)
<dc:identifier opf:scheme="uuid">50f9f8b1-8a81-4dd5-b104-0766188d7d2c</dc:identifier>

[kovidgoyal]

What are these publishers of yours that dont set scheme? In my experience, they all either specify the scheme or prefix with urn:isbn, both of which calibre will handle. In any case, this will handle it: https://github.com/kovidgoyal/calibr...1f76f8f4394382

[davidfor]

Originally Posted by Boilerplate4U

According to the standard specifications the scheme attribute seems optional, this is probably the main reason why so many publishers omit it.

• "https://www.w3.org/Submission/2017/SUBM-epub-packages-20170125/#sec-opf-dcidentifier"
• "http://idpf.org/epub/20/spec/OPF_2.0_final_spec.html#AppendixA" (paragraph 2.2.10)

"The identifier element has an optional OPF scheme attribute defined by this specification. The scheme attribute names the system or authority that generated or assigned the text contained within the identifier element, for example "ISBN" or "DOI." The values of the scheme attribute are case sensitive only when the particular scheme requires it.

This specification does not standardize or endorse any particular publication identifier scheme. Specific uses of URLs or ISBNs are not yet addressed by this specification. Identifier schemes are not currently defined by Dublin Core"

You are correct in that the specs say the scheme is optional. But, it also doesn't say anything about what the identifier is when the scheme is not set. And it seems to be saying that if the identifier has a meaning, that it needs the scheme. But, overall, what you are suggesting is complicating the code to check the identifier against all known schemes when the scheme is omitted. Personally, I think that is a bad idea. And, from my experience, and I suspect from Kovid's based on his response, not at all useful.

[Boilerplate4U]

Originally Posted by kovidgoyal

What are these publishers of yours that dont set scheme? In my experience, they all either specify the scheme or prefix with urn:isbn, both of which calibre will handle. In any case, this will handle it: https://github.com/kovidgoyal/calibr...1f76f8f4394382

Wow, before I even started to think about a practical solution. Many thanks!

[Boilerplate4U]

Originally Posted by davidfor

You are correct in that the specs say the scheme is optional. But, it also doesn't say anything about what the identifier is when the scheme is not set. And it seems to be saying that if the identifier has a meaning, that it needs the scheme. But, overall, what you are suggesting is complicating the code to check the identifier against all known schemes when the scheme is omitted. Personally, I think that is a bad idea. And, from my experience, and I suspect from Kovid's based on his response, not at all useful.

Yeah, the lack of default identifier types sure make it more complex to identify the identifier :-) Kovid's fix now handles "schema"-less isbn ids.