Sustainability factors

The Library of Congress, through its National Digital Information Infrastructure and Preservation Program, has produced a list of Sustainability Factors for the suitability of a digital format for preserving digital information.

Disclosure

"Disclosure refers to the degree to which complete specifications and tools for validating technical integrity exist and are accessible to those creating and sustaining digital content."

The full OpenDocument specification is public, available on the OASIS committee web page and is free to redistribute. As an XML format, any RelaxNG validator can validate OpenDocument files.

The OpenDocument spec is maintained at two open standard organizations (OASIS and ISO).

Adoption

"If a format is widely adopted, it is less likely to become obsolete rapidly, and tools for migration and emulation are more likely to emerge from industry without specific investment by archival institutions."

OpenDocument is adopted by many applications including the major vendors save for Microsoft.

"In some cases, the existence and exploitation of underlying patents may inhibit adoption, particularly if license terms include royalties"

OpenDocument has no patent restrictions, no license restrictions, and no royalties. It can be freely adopted by any software maker including open source software.

Transparency

"Transparency refers to the degree to which the digital representation is open to direct analysis with basic tools, including human readability using a text-only editor."

Transparency is a primary design goal in OpenDocument. Consider this example:

<text:h text:style-name="Heading">
  European Union
</text:h>
<text:p text:style-name="Standard">
  The European Union is a supranational union of 25
  member states from the European continent. It
  was established under that name in 1992 by the
  Treaty on European Union (the Maastricht Treaty).
</text:p>

The format is plain text XML, and the tags are designed to be as human readable as possible.

"Transparency is enhanced if textual content is encoded in standard character encodings (e.g., UNICODE in the UTF-8 encoding)"

OpenDocument text is encoded in Unicode in the UTF-8 encoding.

"compression inhibits transparency... Archival repositories must certainly accept content compressed using publicly disclosed and widely adopted algorithms that are either lossless or have a degree of lossy compression that is acceptable"

In OpenDocument, compression is optional. When compressed, the algorithm used is "ZIP". This is a publicly disclosed, widely adopted, lossless compression algorithm.

Self-documentation

"Digital objects that are self-documenting are likely to be easier to sustain over the long term and less vulnerable to catastrophe than data objects that are stored separately from all the metadata needed to render the data as usable information or understand its context."

OpenDocument is self-documented. Consider this example:

<text:span text:style-name="Strong_20_Emphasis">
   The final years of the twentieth century
   saw the birth of the Internet
</text:span>

The information on how to render the "Strong Emphasis" style is included in the file itself (but elsewhere in the document):

<style:style style:name="Strong_20_Emphasis" 
   style:display-name="Strong Emphasis" 
   style:family="text">
   <style:text-properties fo:font-weight="bold"/>
</style:style>

An ODF document is divided into separate portions including content, metadata and "styles". All the rendering information is stored in styles, which are defined in the styles section of the document.

External dependencies

"External dependencies refers to the degree to which a particular format depends on particular hardware, operating system, or software for rendering or use"

OpenDocument is designed to be platform independent. It does not depend on any particular hardware, operating system or software. Indeed, it is already supported by many applications for at least 8 operating systems (Linux, Windows, Mac, Solaris, FreeBSD, Symbian, OpenBSD, AIX, React OS) and 4 hardware architectures (Sparc, PowerPC, Intel, ARM).

Impact of patents

"Patents related to a digital format may inhibit the ability of archival institutions to sustain content in that format."

OpenDocument comes with no patent restrictions of any kind.

"the existence of patents may slow the development of open source encoders and decoders and prices for commercial software for transcoding content in obsolescent formats may incorporate high license fees"

There are already two open source applications with full support for OpenDocument (OpenOffice.org and KOffice).

Technical protection mechanisms

"Content for which a trusted repository takes long-term responsibility must not be protected by technical mechanisms such as encryption, implemented in ways that prevent custodians from taking appropriate steps to preserve the digital content and make it accessible to future generations."

While ODF files may optionally be encrypted, by default they are not. If encrypted, the encryption follows an industry standard (RFC2898).