Cannot write exif and tiff metadata in image file

Question

Hi,
I have a public XMP text file containing exif and tiff metadata: http://ns.adobe.com/exif/1.0/ and http://ns.adobe.com/tiff/1.0/.
I want to write these XMP data in an image file and it doesn't work. I don't get any exceptions, just the metadata are missing in the image file.
C#
using (var xmpFiles = new XmpFiles())
      if (!xmpFiles.OpenFile("test.jpg", handler.FileFormat, OpenFlags.OpenForUpdate))
          xmpFiles.OpenFile("test.jpg", FileFormat.Unknown, OpenFlags.OpenUsePacketScanning | OpenFlags.OpenForUpdate);
     using (var xmpCore = new XmpCore())
          xmpCore.ParseFromBuffer(xmpPublic.ToString(), ParseFlags.None);
          if (xmpFiles.CanPutXmp(xmpCore))
               xmpFiles.PutXmp(xmpCore);
     xmpFiles.CloseFile(CloseFlags.None);
Public XMP:
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
  <rdf:Description xmlns:_ns_2="http://ns.adobe.com/tiff/1.0/" rdf:about="">
    <_ns_2:ImageLength>4252</_ns_2:ImageLength>
  </rdf:Description>
  <rdf:Description xmlns:_ns_3="http://ns.adobe.com/exif/1.0/" rdf:about="">
    <_ns_3:ApertureValue>8/1</_ns_3:ApertureValue>
  </rdf:Description>
</rdf:RDF>
Result XMP in image file:
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
  <rdf:Description rdf:about=""/>
</rdf:RDF>
Does anyone can help with that problem?
Thanks,
Alexandra

Answer 1

I found the answer by myself.
According to the last guidelines from metadata working group, exif and tiff data should not be saved as XMP data in jpeg images anylonger because jpeg natively supports exif data.
"The most recent (as of mid-2010) XMP specification describes the usage of Exif/TIFF properties within XMP itself. Both Exif ( http://ns.adobe.com/exif/1.0/) and TIFF ( http://ns.adobe.com/tiff/1.0/) namespaces have been defined so that corresponding Exif properties can be stored. This is particularly useful if Exif properties need to be stored but the file format does not support native Exif (e.g. PNG). [...]However, this document changes this earlier XMP guidance and recommends that Exif and Tiff device properties only be mapped into XMP in the case the file format does not support Exif natively."
See http://www.metadataworkinggroup.org/specs