Difference between revisions of "PDF/A in PDS4 - A Primer"
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:* Device-independent color <ref name="FAQ"/> | :* Device-independent color <ref name="FAQ"/> | ||
:* XMP metadata <ref name="FAQ"/> | :* XMP metadata <ref name="FAQ"/> | ||
+ | :** XMP (Extensible Metadata Platform) is an ISO-standardized metadata model created by Adobe. A PDF file contains its metadata in <code><x:xmpmeta></code> tags in XML-based syntax. PDF/A-1 specifies information to be included in this structure, using both predefined XMP schemas and industry-specific XMP extension schemas. | ||
+ | :** From PDFlib: "PDF/A-1 requires XMP for identifying conforming files and supports custom metadata through XMP extension schemas. XMP support in PDF/A-1 is based on the XMP 2004 specification."<ref>XMP Metadata. (n.d.). Retrieved July 07, 2017, from https://www.pdflib.com/knowledge-base/xmp-metadata/</ref> | ||
: PDF/A-1 files '''may not''' include: | : PDF/A-1 files '''may not''' include: | ||
:* Encryption <ref name="FAQ"/> | :* Encryption <ref name="FAQ"/> | ||
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:* This is the much preferred conformance level for PDS4. | :* This is the much preferred conformance level for PDS4. | ||
− | Note that it's not immediately apparent whether a PDF file conforms to a standard. All PDF documents are defined by the same file format, after all, and thus they all use the <code>.pdf</code> filename extension. A document that is intentionally standard-compliant should, however, have metadata which specifies its standard. A file which claims to conform to PDF/A-1a, for example, will include the following tags in the <code>pdfaid</code> namespace: | + | Note that it's not immediately apparent whether a PDF file conforms to a standard. All PDF documents are defined by the same file format, after all, and thus they all use the <code>.pdf</code> filename extension. A document that is intentionally standard-compliant should, however, have XMP metadata which specifies its standard. A file which claims to conform to PDF/A-1a, for example, will include the following tags in the <code>pdfaid</code> namespace: |
{| width=0% | {| width=0% | ||
|<pre> | |<pre> |
Revision as of 20:31, 7 July 2017
PDF/A Overview
The Portable Document Format (PDF) is a broad, complex file format. The International Organization for Standardization (ISO) has created various PDF subset standards which are specialized for different uses. The PDF/A standard (ISO 19005) is designed for long-term preservation. There are three iterations of the PDF/A standard so far: PDF/A-1, PDF/A-2, and PDF/A-3. Versions of PDF/A retain backward but not forward compatibility (e.g., a document that complies with PDF/A-2 will also conform to PDF/A-3, but not necessarily to PDF/A-1). PDS4 requires compliance specifically to the first version, PDF/A-1.[1]
PDF/A-1
PDF/A-1 (ISO 19005-1) is based on PDF Version 1.4, and imposes further specifications.
- PDF/A-1 files must include:
- Embedded fonts [2]
- Device-independent color [2]
- XMP metadata [2]
- XMP (Extensible Metadata Platform) is an ISO-standardized metadata model created by Adobe. A PDF file contains its metadata in
<x:xmpmeta>
tags in XML-based syntax. PDF/A-1 specifies information to be included in this structure, using both predefined XMP schemas and industry-specific XMP extension schemas. - From PDFlib: "PDF/A-1 requires XMP for identifying conforming files and supports custom metadata through XMP extension schemas. XMP support in PDF/A-1 is based on the XMP 2004 specification."[3]
- XMP (Extensible Metadata Platform) is an ISO-standardized metadata model created by Adobe. A PDF file contains its metadata in
- PDF/A-1 files may not include:
There are two levels of conformance:
- PDF/A-1b — Level B (Basic) Conformance
- This is the minimum conformance level required for PDS4.
- PDF/A-1a — Level A (Accessible) Conformance
- This is the much preferred conformance level for PDS4.
Note that it's not immediately apparent whether a PDF file conforms to a standard. All PDF documents are defined by the same file format, after all, and thus they all use the .pdf
filename extension. A document that is intentionally standard-compliant should, however, have XMP metadata which specifies its standard. A file which claims to conform to PDF/A-1a, for example, will include the following tags in the pdfaid
namespace:
<pdfaid:part>1</pdfaid:part> <pdfaid:conformance>A</pdfaid:conformance> |
A PDF reader may make note of this designation. Adobe Acrobat, in particular, displays a blue banner which states that the file "claims compliance with the PDF/A standard." Regardless, this claim of compliance must be validated. A non-compliant document may incorrectly have metadata indicating compliance; conversely, compliance metadata may be missing from an otherwise compliant document.
See Also
External Links
- General
- Backend
References
- ↑ Policy on Formats for PDS4 Data and Documentation. (2014, June 30). The Planetary Data System. From PDS Policies
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 19005-1 FAQ. (2006, July 10). PDF/A Joint Working Group. From NPES PDF/A FAQ
- ↑ XMP Metadata. (n.d.). Retrieved July 07, 2017, from https://www.pdflib.com/knowledge-base/xmp-metadata/