Tim Cook wrote:
> Paul Fuller wrote:
>> "Names are fickle, Identifiers are permanent"
> 
> The problem with tagging is that either a) it stores the data in an
> external database that doesn't follow the file when you copy it to a new
> medium or b) it alters the file, changing its MD5 hash and making it not
> identical to the other copies of it on the internet (or wherever), so
> it's harder to find duplicates in large sets of files or quickly
> determine which images of an existing set are missing.

for a) If you copy all the files to a new medium, copy the database along.
If you send just one file to someone, use a script that reads metadata from
the database and puts it on the filename before sending.

for b) Other people may also use tagging, or recompress a JPEG image, or
[...] which would already make your pictures have a different MD5 from
theirs. Use a real image comparison algorithm if you want to compare.

And in Windows, a lot of metadata may be stored in "alternate data streams"
instead of EXIF or something similar inside the file itself.

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