PDF/A1A & PDF/A1B inavlid due to title => xmp.metadata missing language attribute at <dc:title><rdf:Alt><rdf:li>Title...

[speckyspooky]

I created pdf documents with the conformance of PDF/A1A and PDF/A1B with our BIRT engine.
The results was check on my side with veraPDF and the result is that the PDF/A-versions are unvalid due to an issue with the dc:title.

The problem ist that the language-attribute is missing on rdf:title
and therefore the PDF/A will be marked like invalid.

For the PDF/A-creation I used the default options which was given on openPDF.

The current PDF/A structure is:

      <dc:title>
        <rdf:Alt>
          <rdf:li>Titel-Subtitel</rdf:li>
        </rdf:Alt>
      </dc:title>

The structur shall be:

      <dc:title>
        <rdf:Alt>
          <rdf:li xml:lang="x-default">Titel-Subtitel</rdf:li>
        </rdf:Alt>
      </dc:title>

[andreasrosdal]

Hello @speckyspooky
Would you be interested in contributing support for PDF/A support in OpenPDF? See #980 and https://en.wikipedia.org/wiki/PDF/A.
As suggested this can be implemented with new PdfADocument and PdfAWriter classes for PDF/A support.

[asturio]

Contributions to OpenPDF are welcome.