Sustainability of Digital Formats
 Planning for Library of Congress Collections

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Identification and description

Full name	ISO 19005-1. Document management - Electronic document file format for long-term preservation - Part 1: Use of PDF 1.4, Level A Conformance (PDF/A-1a)
Description	Part 1 of the PDF/A ISO standard [ISO 19005-1:2005] is a constrained form of Adobe PDF version 1.4 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-1a) indicates complete compliance with the ISO 19005-1 requirements, including those related to structural and semantic properties of documents. Level B conformance (PDF/A-1b) indicates minimal compliance to ensure that the rendered visual appearance of a conforming file is preservable over the long term. See PDF/A-1.
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_4, PDF 1.4
Subtype of	PDF/A-1, PDF for Long-term Preservation, Use of PDF 1.4

Local use

LC experience or existing holdings	See PDF/A-1.
LC preference	See PDF/A-1.

Sustainability factors

Disclosure	See PDF/A-1.
Documentation	See PDF/A-1.
Adoption	See PDF/A-1.
Licensing and patents	See PDF/A-1.
Transparency	See PDF/A-1.
Self-documentation	See PDF/A-1.
External dependencies	See PDF/A-1.
Technical protection considerations	See PDF/A-1.

Quality and functionality factors

Text
Normal rendering	See PDF/A-1.
Integrity of document structure	PDF/A-1a requires representation of the logical structure of the document as specified in section 6.8 of ISO 19005-1. The standard recommends that creators "should attempt to capture a document's logical structure hierarchy to the finest granularity possible." Nevertheless, the standard also indicates that "PDF/A-1 writers should not add structural or semantic information that is not explicitly or implicitly present in the source material solely for the purpose of achieving conformance." Hence, the logical structure of a document will only be represented to the degree the creator or process during creation takes steps to incorporate relevant structural tagging.
Integrity of layout and display	See PDF/A-1.
Support for mathematics, formulae, etc.	See PDF/A-1.
Functionality beyond normal rendering	Level A conformance with PDF/A-1 requires that images have alternate text descriptions. The natural language in which the document is written must be declared, and sections of text in other languages explicitly marked using an internal mechanism defined for PDF 1.4. Also see PDF/A-1.

File type signifiers

Tag	Value	Note
Filename extension	pdf	The standard does not indicate that a different extension should be used to distinguish PDF from PDF/A.
Other	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-1a file should have the integer value 1 for pdfaid:part and the value "A" for pdfaid:conformance.

Notes

General	See PDF/A-1.
History	See PDF/A-1.

Format specifications

• See PDF/A-1.

Useful references

URLs

• See PDF/A-1.

Books, articles, etc.

• See PDF/A-1.