# pdfx and “undefined control sequence” caused by Subject meta-tag

According to the pdfx documentation it should be possible to add a Subject field to the XMP metadata file. Addition of this field however seems to cause an unexpected error during compilation of the LaTeX source into a PDF/A-1b file (pdfLaTex).

Try to compile the following source:

\documentclass[a4paper, 12pt]{article}
\usepackage[a-1b]{pdfx}
\begin{document}
Hello, World!
\end{document}


\Author{Me}
\Title{Hello, World!}
\Subject{Hello, World! example.}
\Org{Me}
\Keywords{Hello\sep World}


The source compiles without errors after omission of the Subject tag.

Thanks.

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Edit: I found a solution with two patches.

First patch (pdfx.sty):

52c52,53
<  \let\xmpSubject\xmpKeywords
---
> \def\Subject#1{\gdef\xmpSubject{#1}}
>  \let\xmpSubject\@empty


Second patch (pdfa-1b.xmp):

34a35,37
>    <dc:description>
>      <rdf:Alt><rdf:li xml:lang="x-default">\xmpSubject</rdf:li></rdf:Alt>
>    </dc:description>


With this two patches, all is fine (for Subject).

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You may be right, see the following link: pdfa.org/wp-content/uploads/2011/08/… –  Petr Jul 19 '12 at 22:48
@Petr: thanks for this link. –  Paul Gaborit Jul 19 '12 at 23:21

This look like a bug in pdfx: \Subject is documented, but I can find no implementation. Please report it to the authors.

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