XMP in PDF/A
PDF/A requires the use of XMP for identifying PDF documents as conforming to PDF/A-1a or 1b. You can use our custom XMP standards panel to conveniently display standards identification entries for various ISO standards. XMP support in PDF/A-1 is based on the XMP 2004 specification: all properties from predefined schemas in XMP 2004 can directly be used in conforming documents.
The table below summarizes the names, namespace URIs and preferred namespace prefixes for the predefined XMP schemas as defined in XMP 2004. The names and descriptions of all properties in these predefined schemas can be found in the XMP 2004 specification.
schema name and description | namespace URI | preferred namespace prefix |
Adobe PDF schema | "http://ns.adobe.com/pdf/1.3/" | |
Dublin Core schema | "http://purl.org/dc/elements/1.1/" | dc |
EXIF schema for EXIF-specific properties | "http://ns.adobe.com/exif/1.0/" | exif |
EXIF schema for TIFF properties | "http://ns.adobe.com/tiff/1.0/" | tiff |
Photoshop schema | "http://ns.adobe.com/photoshop/1.0/" | photoshop |
XMP Basic Job Ticket schema | "http://ns.adobe.com/xap/1.0/bj" | xmpBJ |
XMP Basic schema | "http://ns.adobe.com/xap/1.0/" | xmp |
XMP Media Management schema | "http://ns.adobe.com/xap/1.0/mm/" | xmpMM |
XMP Paged-Text schema | "http://ns.adobe.com/xap/1.0/t/pg/" | xmpTPg |
XMP Rights Management schema | "http://ns.adobe.com/xap/1.0/rights/" | xmpRights |
XMP extension schemas for PDF/A
While the predefined XMP schemas above cover many general metadata requirements, company- or industry-specific metadata requirements can only be met with custom XMP schemas. For this purpose PDF/A-1 supports the use of so-called extension schemas. An extension schema is a collection of metadata properties for a specific application scenario. In order to make sure that extension schemas can correctly be interpreted in the future, PDF/A-1 requires that a description of all used extension schemas is embedded in the XMP. The so-called extension schema container schema contains the name and description of all properties as well as their XMP data type. This description must be provided in a formal way using the XMP schemas and properties detailed in Technical Corrigendum 1 for PDF/A. The namespaces for extension schema descriptions are summarized in the table below.
schema name and description | namespace URI | required namespace prefix |
PDF/A extension schema container schema | "http://www.aiim.org/pdfa/ns/extension/" | pdfaExtension |
PDF/A field type schema | "http://www.aiim.org/pdfa/ns/field#" | pdfaField |
PDF/A property value type | "http://www.aiim.org/pdfa/ns/property#" | pdfaProperty |
PDF/A schema value type | "http://www.aiim.org/pdfa/ns/schema#" | pdfaSchema |
PDF/A ValueType value type | "http://www.aiim.org/pdfa/ns/type#" | pdfaType |
Sample extension schemas for PDF/A
We provide several sample extension schemas which may serve as a starting point for creating your own PDF/A-conforming extension schemas. They include a human-readable description of the custom XMP schemas and properties, as well as the corresponding machine-readable description according to the rules set forth by PDF/A-1 and Technical Corrigendum 1. The XMP files include the schema description required for PDF/A as well as a sample dataset, i.e. the actual metadata which makes use of the extension schema:
- Machine extension schema 1: a simple schema with a few properties describing hypothetical machinery.
- Machine extension schema 2: similar to the above, but as an additional feature this schema contains a custom XMP property value type "ArticleNumber". The fields comprising this structured type must also be included in the schema description for PDF/A.
- Engineering archive: this schema describes engineering documents which have been archived as PDF/A based on scanned paper documents. The metadata contains details describing the documents (language and reference number) and the scanning process (scan date and name of operator). A corresponding XMP panel for displaying and editing the entries is also available.
Some of these XMP extension schemas for PDF/A-1 are also included in the PDFlib Cookbook, as well as PDFlib code to create PDF/A conforming output which includes the XMP extension schema.
TechNote 0009 (see below) also includes a sample extension schema.
More detailed technical information
As part of our membership in the Technical Working Group of the PDF/A Competence Center we are involved in the preparation of the PDF/A Technical Notes. The following TechNotes published by the PDF/A Competence Center deal with XMP metadata in PDF/A-1:
- Technical Note TN0008: Predefined XMP Properties in PDF/A-1
This TechNote discusses the XMP properties which can be used in PDF/A-1 without using an extension schema. - Technical Note TN0009: XMP Extension Schemas in PDF/A-1
This TechNote explains the construction of XMP extension schema and includes details about XMP syntax requirements. It also contains a full example of an XMP extension schema.
These TechNotes are highly recommended reading for designers and implementors of PDF/A solutions. PDF/A support in PDFlib GmbH products is implemented according to the ISO 19005-1 standard (including Technical Corrigendum 1) as well as the recommendations in TechNotes 0008 and 0009.
Validating XMP extension schemas for PDF/A
Although a specific validation tool for XMP is not publicly available, we highly recommend the RDF validator on the W3C Web site. Since XMP is a subset of RDF it must conform to the RDF syntax rules which are checked by the W3C validator.
PDFlib 7.0.3 is the first product worldwide with support for XMP extension schemas for PDF/A-1. As a result of our involvement in the PDF/A Competence Center (in particular, work on the PDF/A Testsuite) and as a free service to users and vendors interested in PDF/A, PDFlib GmbH offers a free validation service which checks XMP metadata for compliance with the PDF/A-1 standard. The XMP can be supplied as simple text, or embedded in a PDF or PDF/A document (regardless of the conformance status of the document).