Aperture exported IPTC4XMP sidecars not readable by Adobe or PhotoMecanic

Question

I'm exporting some CR2 RAW master files from an Aperture catalog and want to have the IPTC4XMP sidecar files. The resulting xmp files aren't recognised by Adobe DNG Convertor or PhotoMechanic.
The Aperture created xmp files begin
<?xpacket begin='' id=''?>
<x:xmpmeta xmlns:x='adobe:ns:meta/' x:xmptk='XMP toolkit 2.9-9, framework 1.6'>
<rdf:RDF xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#' xmlns:iX='http://ns.adobe.com/iX/1.0/'>
<rdf:Description rdf:about='' xmlns:Iptc4xmpCore='http://iptc.org/std/Iptc4xmpCore/1.0/xmlns/'>
whereas a file created by PhotoMechanic starts
<x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="XMP Core 4.1.1">
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
<rdf:Description rdf:about=""
xmlns:photoshop="http://ns.adobe.com/photoshop/1.0/">
Is the
<?xpacket begin='' id=''?>
meant to be there in the Aperture version?
Whatever, when I create an xmp file using PhotoMechanic I can then go on to convert the RAW CR2 to a DNG with metadata from the xmp. I can't do this using xmp files exported from Aperture: PhotoMechanic shows no metadata as if the xmp wasn't there.
Editing the file and removing the first (and last closing tag!) line <?xpacket begin='' id=''?> doesn't fix this for me.
Running Aperture 3.1 and Mac OS X 10.6.5 on a MacBook Pro.
Can you export readable xmp files?
Thanks!

Answer 1

David:
Thanks for sharing the file (CR2 and XMP) that you were having problems with. This made it possible to track down the issue, though by no means easy. It took me a couple of hours, and the answer was not where I expected to find it. I thought I'd share the process here, so that others might have an idea of how to to trouble-shoot something like this in the future.
When I attempted to view the IPTC Info dialogue in Photo Mechanic for your problem file, I would get the following error message "Error reading caption from photo" message.
When I open in Bridge for CS3, I could see an entry in the Creator field of "David Gordon +44 [rest of your phone number]" Ditto in for Bridge for CS4 and CS5.
When processed the file via ACR that field persisted. However, from our follow up correspondence off list, you identified that as information entered in the camera. Indeed, when I search the XMP, there is no similar entry, so this indeed appears to be the case.
When I viewed the contents of the XMP file in a text editor, I could see many other metadata fields, so there certainly was a problem.
I took the XMP file from an earlier export that I knew worked, and renamed it to match your CR2 file. The metadata for that file displayed without any problems in Photo Mechanic.
I then tried taking the same known exported XMP file, opened it in a text editor and then "cut" the mid section from the BJK05091.XMP file and pasted it into the other. I then renamed so it would be the same as the original CR2. However, this was still not recognized by Photo Mechanic (same error as above). When viewed in Bridge, I got the same result.
I then spent much too much time, inspected the XMP/XML/RDF code, line by line, expecting to find an error in that, but couldn't find any deviations from my example (which contained all the the metadata fields in Aperture... with the Aperture label entered as the value).
That meant I either missed something, or it was some data value in the XMP itself.
So I started swapping in segments from the "good" XMP file into your problem XMP file, and changing the file name of the CR2 to match so that I could then try too open the file in Photo Mechanic.
Finally, in the last segment I found the answer to your mystery....
and the answer is.... &
No, really, the culprit was a couple of Ampersands, those "&" symbols that had been placed into the Usage Rights field before you exported the XMP sidecar.
While the ampersands I had found and replaced with a simple "and" were in the Usage Rights field, they would prevent you from seeing the metadata for the file; regardless of which field they are placed in.
To figure out why that might make a difference, I tried entering an Ampersand "&" into the Caption(Description) field in Photo Mechanic and Bridge. When I inspected the XMP sidecar in a text editor, I found my answer. These applications were using the "&" code!
In HTML the ampersand is assumed to begin an "entity" reference. (see http://htmlhelp.com/reference/html40/entities/ if you really want to know about these).
So it appears that the Apple engineers either made the assumption that no-one would ever enter an ampersand into a metadata field (rookie mistake), or they forgot to write an escape routine into the Aperture software for those times when someone did use an ampersand (and presumably other entity references).
I tried entering a tilde "~" into the XMP from a text editor and that worked just fine. However, greater than ">" and less than "<"&" and other symbols until after you test them out.
Hope that makes your morning!
David