Document created with ConTeXt fails validation

[tarleb]

Validating the file test.pdf, created with ConTeXt, yields the following error:

<validationReport profileName="PDF/A-3A validation profile" statement="PDF file is not compliant with Validation Profile requirements." isCompliant="false">
  <details passedRules="130" failedRules="1" passedChecks="1684" failedChecks="1">
    <rule specification="ISO 19005-3:2012" clause="6.6.2.3" testNumber="7" status="failed" passedChecks="0" failedChecks="1">
      <description>All properties specified in XMP form shall use either the predefined schemas defined in the XMP Specification,
                  ISO 19005-1 or this part of ISO 19005, or any extension schemas that comply with 6.6.2.3.2.</description>
      <object>XMPProperty</object>
      <test>(isPredefinedInXMP2005 == true || isDefinedInMainPackage == true || isDefinedInCurrentPackage == true) &amp;&amp; isValueTypeCorrect == true</test>
      <check status="failed">
        <context>root/document[0]/metadata[0](15 0 obj PDMetadata)/XMPPackage[0]/Properties[2](http://purl.org/dc/elements/1.1/ - dc:description)</context>
        <errorMessage>An XMP property is either not not pre-defined, is not defined in any extension schema, or has invalid type.</errorMessage>
      </check>
    </rule>
  </details>
</validationReport>

The relevant entry in the metadata (retrieved and formatted via pdfinfo -meta test.pdf | tidy -xml -i -q)

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
    <rdf:Description rdf:about=""
    xmlns:dc="http://purl.org/dc/elements/1.1/">
      <dc:format>application/pdf</dc:format>
      <dc:creator>
        <rdf:Seq>
          <rdf:li xml:lang="x-default">AUTHOR</rdf:li>
        </rdf:Seq>
      </dc:creator>
      <dc:description>
        <rdf:Alt>
          <rdf:li xml:lang="x-default" />
        </rdf:Alt>
      </dc:description>
...

I don't understand the problem with this snippet. However, I'm new to the world of PDF/A, so apologies if I misunderstood something and the validation error is actually correct.

[bdoubrov]

The is issue is caused by the extension schema that redefines dc:description as plain Text, while the metadata itself uses Lang Alternate, which is actually the default for the title property in Dublin Core.

Removing the redefinition of dc:title in the extension schema makes the file PDF/A compliant. I'm attaching the modified sample:
test-fixed.pdf

[tarleb]

Ah, that makes sense. Thanks for looking into this and sorry for the noise.