The Apple tags are implemented in the same way that OpenMeta tags are - as extended attributes attached to the files in the filesystem. The only difference is that the attribute name is _kMDItemUserTags instead of kMDItemOMUserTags (the "OM" in the latter tag is for "OpenMeta"). The tag data for both Mavericks tags and OpenMeta tags are property lists, but I didn't look at the internal format of the plists so I don't know if they're exactly the same or not. I also don't know what, if any, auxiliary storage or alternate methods are used for non-HFS+ disk formats - I know Apple's hype said you could tag files on iCloud too, so there may be some issue there.
The long and the short of it, however, is that at least on local Mac disks, the OpenMeta tag data will need to be migrated to the new _kMDItemUserTags attribute in order to be seen natively by Maverick. Not a big deal, but someone needs to write a utility to do that.
- Jon
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