ash of write priority values keyed by group name</td></tr>

<tr><td>WRITTEN</td><td>Hash of tags written (currently used only for filesystem date/time tags)</td></tr>

<tr><td>XMP_CAPTURE</td><td>Hash of tag information (value, attribute hash) keyed by XMP
    property path, used by XMP module during writing</td></tr>

<tr><td>XMP_ERROR</td><td>Error string used by XMP module during writing</td></tr>

<tr><td>XMP_NS</td><td>Hash of URI's keyed by namespace prefix, used by XMP module
    during writing to re