XMP Specification
The following specifications are included in the XMP Toolkit zip package. They are available here for convenient reference.The specification is provided under the XMP Specification Public Patent License (PDF, 28 K).
Part 1, Data model, Serialization, and Core Properties (PDF, 499K) [April, 2012] covers the basic metadata representation model that is the foundation of the XMP standard format. The Data Model prescribes how XMP metadata can be organized; it is independent of file format or specific usage. The Serialization Model prescribes how the Data Model is represented in XML, specifically RDF.
Part 1 is also covered as part of ISO 16684-1:2012, Graphic technology – Extensible metadata platform (XMP) specification – Part 1: Data model, serialization and core properties. You can read more about it here and access the standard from the ISO Store.
Part 2, Additional Properties (PDF, 383K) [Aug, 2016] provides detailed property lists and descriptions for standard XMP metadata schemas; these include general-purpose schemas such as Dublin Core, and special-purpose schemas for Adobe applications such as Photoshop. It also provides information on extending existing schemas and creating new schemas.
Part 3, Storage in Files (PDF, 1.4M) [Jan, 2020] provides information about how serialized XMP metadata is packaged into XMP Packets and embedded in different file formats. It includes information about how XMP relates to and incorporates other metadata formats, and how to reconcile values that are represented in multiple metadata formats.
Description of XMP schemas using RELAX NG [Dec, 2014] is a ISO 16684-2:2014 standard which specifies the use of RELAX NG to describe serialized XMP metadata. This applies to how conforming schemas can use the features of RELAX NG. This standard is published as ISO 16684-2:2014 Graphic technology – Extensible metadata platform (XMP) – Part 2: Description of XMP schemas using RELAX NG.