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ISO 16684-4

Extensible metadata platform (XMP) – Part 4: Use of XMP for semantic units

This document broadens the concept of XMP specified in ISO 16684-1 so that XMP can be used to describe semantic units (SU). A new flexible way of defining and describing SUs aims to bring innovation to textual and non-textual content, metadata, linked data, big data and artificial intelligence.

  • introduces the concept of the semantic unit;
  • provides requirements and guidance on how to define the target resource(s) in an SU by adopting the “target” syntax from the Web Annotation Model;
  • provides requirements and guidance on the extensible metadata platform (XMP) serialization syntaxes for SU.

For more information, refer to the PDF Association’s Technical Resources.


Technical questions about ISO 16684 are most effectively addressed in the PDF Association’s official pdf-issues GitHub repo.


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ISO Group Responsible: ISO TC171 SC2 WG12

ISO Status: status of all PDF-related ISO work


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