IPTCDigest

[ScannerBoy]

@StarGeek: In an answer to my earlier post, you stated

If the XMP data is important and in sync with the IPTC, then you would want to update it because otherwise the XMP data will be ignored if the program honors the IPTCDigest tag. Note that this is can be extremely important if the program follows the character limitations of the IPTC IIM data. An example would be Adobe Bridge, which obeys the character limitation (I do not know if this applies to other Adobe programs). If I set the "Sublocation" to Palais des Festivals et des Congrès, then Bridge will truncate the IPTC data. So it would be important to use the XMP data over the IPTC data.
Code Select
C:\>exiftool -G1 -a -s -*location* y:\!temp\Test4.jpg
[XMP-iptcCore]  Location                        : Palais des Festivals et des Congrès
[IPTC]          Sub-location                    : Palais des Festivals et des Cong

Your reply seems to based on an Adobe app.
Is there a app which does validation for a specific image or other file with metadata, other than possibly some Adobe apps?
I have seen a number of comments related to the replacement of the old IPTC data with one or other of the XMP subsections. Is there any documentation on the requirements and logic on how to correct/handle/fix any bad/missing/misplaced data?
I would assume it might be included as part of the app's logic in some of the apps from Adobe, but since all of those seem to be commercial only, there seem to be no readily accessible verification app, without a seemingly large and on-going investment.
As well, I know of a number of other apps/DAMs which claim to do error and compliance checking, but I have not seen any compliance tester app to verify their claim in this respect.
Of course, many offer a free trial period, but that time will most likely be insufficient to actually accomplish this verification.

My goal for my own effort in this direction is to look for something along the lines of a spell checker. It will need a clear set of rules as to the 'correct' usage of "words'/tags' and attached information, advise the user when the 'data' used does not follow the given rules and then give the user the option to either ignore the presented options or apply the 'fixes' for the specific case.

A question I had forgotten to add: Does the new XMP data have an equivalent Digest/checksum field to check whether the XMP data has been modified?