Sustainability of Digital Formats: Planning for Library of Congress Collections

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Portable Embosser Format

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name Portable Embosser Format

Largely considered a legacy format as of this writing in 2024, the specification defines the Portable Embosser Format (PEF) as "a document type that represents braille pages in digital form, accurately and unambiguously; regardless of language, location, embosser settings, braille code and computer environment." The goal of the format is to enable a "completely automated reproduction of advanced braille books." The format is intended to be used for braille embossing and archiving irregardless of how the braille was produced. PEF supports features like ink overlay and tactile graphics. Structurally, PEF is a Unicode-encoded, XML-based document format. Comments welcome.

Production phase According to the specification, PEF is a delivery and archive format.
Relationship to other formats
    Extension of XML, XML (Extensible Markup Language)
    Affinity to Open Braille Formatting Language. Working draft by the same author. Not described on this site at this time.

Local use Explanation of format description terms

LC experience or existing holdings None.
LC preference

The National Library Service for the Blind and Print Disabled (NLS) at the Library of Congress includes a list of braille embossers but the use of PEF is not specifically called out.

The Library of Congress Recommended Formats Statement has not yet expressed any format preference for braille content.

Sustainability factors Explanation of format description terms

Disclosure Fully disclosed.

" PEF 1.0 - Portable Embosser Format". Joel Håkansson, et al. Public draft, revised 12 September 2011.

The DAISY Consortium hosted a working draft document (link via Internet Archive) that is no longer updated. It was replaced by the PEF Format website (link via Internet Archive), which is also defunct. All three of these documents generally cover the same content, worded in slightly different ways.

It is unclear if there has been any active support since 2011. Comments welcome.


The American Foundation for the Blind states that PEF is used in Scandinavia but it has not gained wide popularity and is rarely used in the United States.

Considered a "popular format" by media remediation service SensusAccess along with Unicode, UTF8, and NACB (North American Computer Braille). Additional details are available through the Producing Braille with SensusAccessBraille with SensusAccess

    Licensing and patents No patents or licensing. Comments welcome.
Transparency XML-based format can be read without using advanced tools. May require some advanced knowledge and potentially hardware equipment (embossers) to implement.

According to the specification, a PEF file uses DublinCore to hold descriptive metadata. The format and identifier fields are mandatory. The following fields are optional: title, creator, subject, description, publisher, contributor, date, type, source, language, relation, coverage, and rights.

The <head> section of the format can also be extended to include additional metadata fields.

External dependencies None.
Technical protection considerations None.

Quality and functionality factors Explanation of format description terms

Normal rendering PEF represents braille pages in digital form.
Integrity of document structure PEF supports formatting to fit particular paper sizes, optional pagination and optional duplex embossing.
Integrity of layout and display PEF relies on Unicode to accurately represent characters.
Support for mathematics, formulae, etc. Not supported.
Functionality beyond normal rendering PEF can define features such as ink overlay or tactile graphics.

File type signifiers and format identifiers Explanation of format description terms

Tag Value Note
Filename extension pef
The specification states: "It is recommended that PEF files have the extension ".pef" (all lowercase) on all platforms.
Internet Media Type application/x-pef+xml
The specification states: "The Internet media type for PEF is "application/x-pef+xml". The specification also notes the dc:format field must have the value "application/x-pef+xml"
Magic numbers See related format.  See XML.
XML namespace declaration See note.  The root element of the document must be in the PEF namespace. The start tag of the root element of the document must contain an xmlns declaration for the PEF namespace [XMLNS]. The namespace URI for PEF 1.0 is defined as "". An example root element might look like: <pef version="2008-1" xmlns="">". See the specification for more details.
Pronom PUID See note.  PRONOM has no corresponding entry as of April 2024.
Wikidata Title ID Q105864558

Notes Explanation of format description terms


The format was developed by researchers at the Swedish Library for the Blind in 2008 in conjunction with the DAISY Consortium.

Format specifications Explanation of format description terms

Useful references


Last Updated: 05/14/2024