need setProperty syntax for XMP object

Question

I am randomly generating DocumentID and InstanceID, but facing problem in setting property DocumentID and InstanceID to the xmp object.

How can I set the generated DocumentID and InstanceID to my allXMP?

var xmpFile = new XMPFile(linkFilepath, XMPConst.FILE_INDESIGN, XMPConst.OPEN_FOR_UPDATE);
var allXMP = xmpFile.getXMP();

// Retrieve values from external links XMP.
var documentID = allXMP.getProperty(XMPConst.NS_XMP_MM, 'DocumentID', XMPConst.STRING);
var instanceID = allXMP.getProperty(XMPConst.NS_XMP_MM, 'InstanceID', XMPConst.STRING);

documentID =  randomString(32);
instanceID = randomString(32);

// ???? Here I need to set DocumentID and InstanceID to allXMP

if (xmpFile.canPutXMP(allXMP)) {     
    xmpFile.putXMP(allXMP);    
    xmpFile.closeFile(XMPConst.CLOSE_UPDATE_SAFELY);     
} 

Answer 1

You can utilize the setProperty() method in the AdobeXMPScript library to create and set the value for DocumentID and InstanceID

Below are a couple of helper functions for adding a DocumentID and InstanceID.

// Note: This function works on macOS only
function generateUUID() {
  var cmd = 'do shell script "uuidgen | tr -d " & quoted form of "-"';
  return app.doScript(cmd, ScriptLanguage.applescriptLanguage);
}

// Add an XMP property and Value.
function addXmpPropertyAndValue(filePath, xmpProperty, xmpValue) {
  var xmpFile = new XMPFile(filePath, XMPConst.FILE_UNKNOWN, XMPConst.OPEN_FOR_UPDATE);
  var allXMP = xmpFile.getXMP();

  allXMP.setProperty(XMPConst.NS_XMP_MM, xmpProperty, xmpValue);

  if (xmpFile.canPutXMP(allXMP)) {
    xmpFile.putXMP(allXMP);
  }

  xmpFile.closeFile(XMPConst.CLOSE_UPDATE_SAFELY);

  // Useful for testing purposes....
  alert('Added: ' + xmpProperty + '\n' +
      'value: ' + xmpValue + '\n\n' +
      'Path: ' + filePath, 'Updated XMP', false);
}

To add an instanceID invoke the addXmpPropertyAndValue function as follows:

// The `linkFilepath` argument should be the filepath to the Link you want to update
addXmpPropertyAndValue(linkFilepath, 'InstanceID', 'xmp.iid:' + generateUUID());

To add an DocumentID invoke the addXmpPropertyAndValue function as follows:

// The `linkFilepath` argument should be the filepath to the Link you want to update
addXmpPropertyAndValue(linkFilepath, 'DocumentID', 'xmp.did:' + generateUUID());

---

Additional Note:

When generating the value(s) for DocumentID and InstanceID the guidelines state:

An ID should be guaranteed to be globally unique (in practical terms, this means that the probability of a collision is so remote as to be effectively impossible). Typically 128- or 144-bit numbers are used, encoded as hexadecimal strings

^{The excerpt (above) can be found on page 19 of Partner's guide to XMP for Dynamic Media (PDF)}

Unfortunately, ExtendScript does not provide a built-in feature to generate a globally unique identifier (GUID). However macOS does include uuidgen which is a command-line utility/library for generating unique identifiers (UUID/GUID).

The helper function (above):

function generateUUID() {
  var cmd = 'do shell script "uuidgen | tr -d " & quoted form of "-"';
  return app.doScript(cmd, ScriptLanguage.applescriptLanguage);
}

runs on macOS only. It utilizes AppleScript to run the uuidgen command.

You may want to generate the identifier this way instead of your current randomString(32) function call.