Hello list,

The following document fails PDF/A-3a validation. It passes without the attachment.

\setuplanguage       [en]
\setuptagging        [state=start]
\setupinteraction    [state=start]
\setupbackend        [format={pdf/a-3a},profile={default_gray.icc},
                      intent={ISO coated v2 300\letterpercent\space (ECI)}]
\setupstructure      [state=start,method=auto]
\setupcolors         [pagecolormodel=auto,start=yes,rgb=no,cmyk=no]
\setupbodyfont       [Palatino,10pt]
\starttext

  Attaching a plain text file.

% \attachment        [file=test.tex,
%                     type={text/plain;charset=UTF-8}]
% The \ConTeXt\ source code for this document is attached here.
  \attachment        [file=testa.pdf,
                      type={application/pdf}]
  A successfully validated pdf/a-3a file is attached here.

\stoptext

pdf-online reports:

Validating file "test.pdf" for conformance level pdfa-3a
The key F is required but missing.
The appearance dictionary doesn't contain an entry.
File specification 'testa.pdf' not associated with an object.
The document does not conform to the requested standard.
The document doesn't conform to the PDF reference (missing required entries, wrong value types, etc.).
The document contains hidden, invisible, non-viewable or non-printable annotations.
The document contains annotations or form fields with ambigous or without appropriate appearances.
The document does not conform to the PDF/A-3a standard.
Done.