How do I edit image metadata?

Question

What I would like to be able to do is something like:
  tell application "Image Events"
  tell pic
    make new metadata tag with properties {name:"creation", value:cr}
  end tell
  end tell
Only, sips/Image Events doesn't support setting most image metadata. Any suggestions as to how to approach this problem?

Answer 1

Thanks. Lightroom 2.4, unfortunately, isn't very scriptable. This is ironic, since the program itself relies on Lua for its interface functionality. I will probably, eventually, manage to compile Exempi and the Python XMP Toolkit and do the job that way.
Refs:
  [Exempi|http://libopenraw.freedesktop.org/wiki/Exempi]
  [Python XMP Toolkit|http://www.spacetelescope.org/projects/python-xmp-toolkit/docs/index.ht ml]