Get Media Management Metadata

The xmpMM: namespace is how XMP tracks document identity across saves, conversions and renditions. Document.GetMediaManagement returns it as an xmputil.MediaManagement. Read it when you need to know whether two files are the same document, or what a file was derived from.

Three identifiers do the work, and they change at different rates:

Doing it

xmpDoc, err := xmputil.LoadDocument(stream.Stream)
if err != nil {
    return err
}

mm, ok := xmpDoc.GetMediaManagement()
if !ok {
    fmt.Println("no xmpMM namespace in this document")
    return nil
}

fmt.Println(mm.OriginalDocumentID, mm.DocumentID, mm.InstanceID, mm.VersionID)

The stream comes from reader.GetCatalogMetadata and core.GetStream, as in get XMP metadata.

DerivedFrom is a *MediaManagementDerivedFrom and is nil when the document is not recorded as derived from anything. It is a partial reference by design: the components it does carry, usually an instance ID and a version, point at the source, and anything missing is assumed unchanged.

Versions is the edit history, each entry holding VersionID, ModifyDate, Comments and Modifier. It is empty in most files.

Limitations

Every identifier is a xmputil.GUID, which is a string type. Compare them as strings, and treat an empty value as absent rather than as a zero GUID.

SetMediaManagement does not write version history, so a non-empty Versions means the packet came from a tool that records it. Reading the field back after writing with UniPDF will give you nothing.

The identifiers only mean what the producing application made them mean. A tool that rewrites a file without updating InstanceID leaves you unable to tell two versions apart, and a tool that regenerates DocumentID on every save destroys the branch relationship. Treat the values as evidence, not proof.

Run the example

The example prints all of the xmpMM: fields it finds, including the derivation reference and any version history.

git clone https://github.com/unidoc/unipdf-examples.git
cd unipdf-examples/metadata
go run pdf_get_xmp_media_management_metadata.go input.pdf

If this is your first time using UniPDF, follow the getting started guide to create an API key and set up your development environment.