The "Use XML Info Only" option
Occasionally, a user's iPhoto library can get to a point where, due to either some sort of corruption in the iPhoto library's data, or just from a library having too many files for the machine to handle well, doing anything in iPhoto can become exceptionally slow or cause iPhoto to crash. This is, of course, exactly the situation in which many people want to use iPhoto Library Manager to get their libraries into a more managable setup, usually by splitting the library into multiple smaller libraries. However, if the iPhoto library has gotten bad enough, iPhoto's slowness can interfere with the normal operation of iPhoto Library Manager, making it impossible to effectively split your library up.
For these types of situations, iPhoto Library Manager offers an option (in the "Photo Copying" tab of the preferences window) to use the library's AlbumData.xml file to retrieve information about the library instead of opening up and retrieving the information through Applescript. This allows you to copy albums or merge libraries without ever opening the troublesome library. The necessary information is read directly from the AlbumData.xml file, and the photos are copied into the new library, avoiding having to deal with iPhoto's slowness or crashing.
Why not use this option all the time then? Because, the AlbumData.xml file does not contain all of the various metadata that iPhoto Library Manager normally retrieves when copying photos. The normal transfer method is still the most complete way to go, but the XML info method is usually good enough when the normal mode doesn't work
More recent versions of iPhoto write out more information to the AlbumData.xml file that previous versions. The specific information that is not available for each version is:
- iPhoto 7: all metadata is copied, but photos marked as hidden in iPhoto will not be copied
- iPhoto 6: album comments and roll dates
- iPhoto 5.0.2 through 5.0.4: album comments and roll dates, names, and comments
- iPhoto 4.0.3 through 5.0.1: album comments and all roll organization. Instead of photos being imported in the same roll organization as the source library, they will instead be grouped into rolls as they are in the library's albums, similar to the "One roll per album" option when copying albums.