Subject: [Uri-review] xmp.did xmp.iid scheme registration

From: Larry Masinter <[email-masked]>
Date: Wed, 18 Oct 2017 06:44:12 +0000

Should have done this 10 years ago. There are two schemes, with identical templates.

 Scheme name:

     xmp.iid

     xmp.did

   Status:

      Provisional (?)

   Applications/protocols that use this scheme name:

     Many products from Adobe and others

   Contact:

     Larry Masinter <[email-masked]<mailto:[email-masked]>>

   Change controller:

     Adobe

   References:

     “Partner’s Guide to XMP for Dynamic Media”, 2008

     https://wwwimages2.adobe.com/content/dam/Adobe/en/devnet/xmp/pdfs/DynamicMediaXMPPartnerGuide.pdf#page=19

      page 19 (reproduced below)

    Security Considerations

      These identifiers are used in data

      structures that track the provenance
      of works. This information might

      be considered private, but if stripped

      the utility is reduced.

Identifier URI schemes
The following URI schemes are used in some versions of XMP software to ensure unambiguous ID
references:
➤ xmp.iid: Used for InstanceID
➤ xmp.did: Used for DocumentID
These have the same syntax as InstanceID and DocumentID; globally unique 128-bit numbers
encoded in hexadecimal. However, each is used only in the correct context. For example, the
following unambiguously refers to “a file that has this ID as its InstanceID in its XMP Packet”:
xmpMM:InstanceId="xmp.iid:b9db20421f30bb3fe10e5f90"
Similarly:
xmpMM:DocumentId="xmp.did:b9db20421f30bb3fe10e5f90"
xmpMM:OriginalDocumentId="xmp.did:b9db20421f30bb3fe10e5f90"
The xmp.iid and xmp.did URIs are used only for files that have XMP actually stored in the file, not in
sidecar files. Files that do not have embedded XMP still have InstanceID and DocumentID, but not in
this form. Some documents that do have embedded XMP might still have a DocumentID that does not
use xmp.did, because the document started out as a file without XMP but with some other kind of
unique document identifier.
These are URIs (that is, they uniformly identify resources), but they are only useful as URLs (Uniform
Resource Locators) if there is an index of files with XMP indexed by the IDs found within them. In the
case of xmp.did:, it might be necessary to examine modification dates and history to determine which
is the latest of multiple instances with the same document ID.