Which is a very easy to do if one uses a real digital signature.
A real digital signature has absolutely no "corrective" effect if the problem to be solved is described in this way:
The appraiser is obligated by assignment conditions to upload his file into conversion software before transmission. That act of uploading places imbedded objects into the file. Some of those imbeded objects cause changes to the appearance of the file on the appraisers' screen viewer and others of those objects don't do
anything until the receiver opens the file in their own,
different viewer.
The appraiser says his true copy is what he saw on his screen, the receiver says the true copy is what he saw on his screen. But the two parties are not seeing the same thing because some of those imbedded objects aren't activated on the appraisers' viewer, only on the receivers' viewer.
At some point, it becomes important either at a state board or in court to determine which version is the true copy. Regardless which version is ultimately determined to be the true version, the fact will remain that there was never any chance that both parties would have posession of the true copy, only one of them will.
The difference a vault would make is that an appraiser could deliver a universal PDF to a vault. Subsequently, the appraiser could retreive the true copy from the vault. Then the client could retreive the true copy from the vault. Then the board or the court could retreive the true copy from the vault.
Everyone would have a common understanding of what the true copy was. If the receiver chose to retreive the file from the vault and open it in such a way as to view it differently, then everyone involved would know that he specificall chose not to look at the true copy before making his lending decision. the onus would be on him and the appraiser could not be accused of complicity.
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The only apples to apples comparison to a non-vault scheme would be for clients to discontinue the practice of requiring the conversion to take place on the appraisers' computer. The appraiser could send all files as a universal PDF and transmit it in a digital signature.
In both cases, vault or digital signature, the "other agenda" of the appraiser is to be relieved of having to do an
unknowable conversion prior to transmission.
But only the vault scheme gives third parties a benchmark as to what the true copy is.
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This touches on the root of the "other agenda" on both sides.
The client wants to make the appraiser responsible for all of the conversion.
The appraiser doesn't want to be responsible for any part of the conversion that is
unknowable, that he can't see or can't understand including any/all imbedded objects that he doesn't even know are there.
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There are more "other agendas" on both sides but these are the ones associated with the idea of the vault.