Sustainability of Digital Formats: Planning for Library of Congress Collections
Sustainability of Digital Formats: Planning for Library of Congress Collections |
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | ISO 19005-2. Document management - Electronic document file format for long-term preservation - Part 2: Use of ISO 32000-1 (PDF 1.7), Level A Conformance (PDF/A-2a) |
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| Description |
Part 2 of the PDF/A ISO standard [ISO 19005-2:2010] is a constrained form of Adobe PDF version 1.7 intended to be suitable for long-term preservation of page-oriented documents for which PDF is already being used in practice. Level A conformance (PDF/A-2a) indicates complete compliance with the ISO 19005-2 requirements, including those related to structural and semantic properties of documents. Level B conformance (PDF/A-2b) indicates minimal compliance to ensure that the rendered visual appearance of a conforming file is preservable over the long term. Level U conformance (PDF/A-2u) represents Level B conformance with the additional requirement that all text in the document have Unicode equivalents. See PDF/A-2. |
| Production phase | A final-state format for delivery to end users and long-term preservation of the document as disseminated to users. |
| Relationship to other formats | |
| Subtype of | PDF, Portable Document Format |
| Subtype of | PDF_1_7, PDF, Version 1.7 (ISO 32000-1:2008) |
| Subtype of | PDF/A-2, PDF for Long-term Preservation, Use of ISO 32000 (PDF 1.7) |
| Affinity to | PDF/UA-1, PDF Enhancement for Accessibility, Use of ISO 32000-1. The requirements for accessibility and for level A conformance with PDF/A-2 are largely compatible. One significant distinction is that in PDF/UA content can be encrypted, while for PDF/A (intended for long-term archiving) encryption is prohibited. |
| LC experience or existing holdings | See PDF/A_family. |
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| LC preference | See PDF/A_family. |
| Disclosure | See PDF/A-2. |
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| Documentation | See PDF/A-2. |
| Adoption | See PDF/A-2. |
| Licensing and patents | See PDF/A_family. |
| Transparency | See PDF/A_family. |
| Self-documentation | See PDF/A_family. |
| External dependencies | See PDF/A_family. |
| Technical protection considerations | See PDF/A_family. |
| Text | |
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| Normal rendering | See PDF/A_family. |
| Integrity of document structure | PDF/A-2a includes representation of the logical structure of the document, as specified in section 6.8 of ISO 19005-2, in addition to the retention of visual rendering. |
| Integrity of layout and display | See PDF/A_family. |
| Support for mathematics, formulae, etc. | See PDF/A_family. |
| Functionality beyond normal rendering | See PDF/A_family. |
| Tag | Value | Note |
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| Filename extension | pdf |
The standard does not indicate that a different extension should be used to distinguish PDF from PDF/A. |
| Internet Media Type | See related format. | See PDF. |
| Magic numbers | See related format. | See PDF. |
| Indicator for profile, level, version, etc. | See note. | The standard specifies that the PDF/A version and conformance level of a file shall be specified using the PDF/A Identification extension schema defined in the standard. This schema has two mandatory elements: pdfaid:part and pdfaid:conformance. A PDF/A-2a file should have the integer value 2 for pdfaid:part and the value "A" for pdfaid:conformance. |
| Pronom PUID | fmt/476 |
See https://www.nationalarchives.gov.uk/PRONOM/fmt/476 for PDF/A-2a. |
| Wikidata Title ID | Q26545877 |
See https://www.wikidata.org/wiki/Q26545877 for PDF/A-2a. |
| General |
Requirements for accessibility and for level A conformance with PDF/A-2 are very compatible. PDF/UA's mandatory representation of the logical structure of a document to support non-visual navigation should provide excellent support for future use of a document by automated tools, including migration to new formats and new versions of formats. One significant distinction is that in PDF/UA content can be encrypted, while for PDF/A (intended for long-term archiving) encryption is prohibited. See also PDF/A-2. |
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| History | See PDF/A-2. |
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