ISO/TR 18492:2005
(Main)Long-term preservation of electronic document-based information
Long-term preservation of electronic document-based information
ISO/TR 18492:2005 provides practical methodological guidance for the long-term preservation and retrieval of authentic electronic document-based information, when the retention period exceeds the expected life of the technology (hardware and software) used to create and maintain the information. It takes into account the role of technology-neutral information technology standards in supporting long-term access. This guidance also acknowledges that ensuring the long-term preservation and retrieval of authentic electronic document-based information should involve IT specialists, document managers, records managers and archivists. ISO/TR 18492:2005 does not cover processes for the creation, capture and classification of authentic electronic document-based information. This Technical Report applies to all forms of information generated by information systems and saved as evidence of business transactions and activities.
Conservation à long terme d'information document-basée électronique
General Information
Standards Content (Sample)
TECHNICAL ISO/TR
REPORT 18492
First edition
2005-10-01
Long-term preservation of electronic
document-based information
Conservation à long terme d'information document basée électronique
Reference number
ISO/TR 18492:2005(E)
©
ISO 2005
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ISO/TR 18492:2005(E)
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ISO/TR 18492:2005(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope .1
2 Normative references .1
3 Terms and definitions .2
4 Symbols and abbreviated terms .3
5 Long-term preservation .3
5.1 General.3
5.2 Goals of a long-term preservation strategy .4
6 Elements of a long-term preservation strategy .7
6.1 General.7
6.2 Media renewal .7
6.3 Metadata .10
6.4 Migrating electronic document-based information.11
7 Developing a long-term preservation strategy .14
7.1 Long-term preservation policy.14
7.2 Quality control.14
7.3 Security.15
7.4 Environmental control and monitoring .16
Annex A (informative) National electronic records programmes and other selected publications .17
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ISO/TR 18492:2005(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In exceptional circumstances, when a technical committee has collected data of a different kind from that
which is normally published as an International Standard (“state of the art”, for example), it may decide by a
simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely
informative in nature and does not have to be reviewed until the data it provides are considered to be no
longer valid or useful.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO/TR 18492 was prepared by Technical Committee ISO/TC 171, Document management applications,
Subcommittee SC 3, General issues.
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ISO/TR 18492:2005(E)
Introduction
Ensuring the long-term preservation of authentic electronic document-based information is a well-documented
and identified problem within many fields of expertise, including archival science, document management,
e-commerce, e-governance and technology development. As an additional problem, individuals and
organizations charged with the responsibility for ensuring long-term access to authentic electronic
document-based information have employed a diversity of strategies designed to achieve this goal.
Although there is a clear need to address the problem of long-term access to authentic electronic
document-based information, there is a current lack of harmonized international guidance on these issues.
This has led to diverse and, sometimes, incompatible approaches that can give rise to potentially
mission-critical problems, regarding the accessibility and/or authenticity of the electronic document-based
information being retained.
Acknowledging the generic technological obsolescence problem of computer hardware and software as well
as the limited life of digital storage media, this Technical Report provides guidance to storage repositories in
providing access to and maintaining authentic electronic document-based information that has been retained
for future reference.
The purpose of this Technical Report is to provide a clear framework for strategy development and best
practices that can be applied to a broad range of public and private sector electronic document-based
information to ensure its long-term accessibility and authenticity.
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TECHNICAL REPORT ISO/TR 18492:2005(E)
Long-term preservation of electronic document-based
information
1 Scope
This Technical Report provides practical methodological guidance for the long-term preservation and retrieval
of authentic electronic document-based information, when the retention period exceeds the expected life of
the technology (hardware and software) used to create and maintain the information.
It takes into account the role of technology neutral information technology standards in supporting long-term
access.
This guidance also acknowledges that ensuring the long-term preservation and retrieval of authentic electronic
document-based information should involve IT specialists, document managers, records managers and
archivists.
It does not cover processes for the creation, capture and classification of authentic electronic document-based
information.
This Technical Report applies to all forms of information generated by information systems and saved as
evidence of business transactions and activities.
NOTE Electronic document-based information constitutes the “business memory” of daily business actions or events
and enables entities to later review, analyse or document these actions and events. As such, this electronic
document-based information is evidence of business transactions that enable entities to support current and future
management decisions, satisfy customers, achieve regulatory compliance and protect against adverse litigation. To
achieve this goal, this electronic document-based information should be retained and appropriately preserved.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 12651:1999, Electronic imaging — Vocabulary
ISO 15489-1, Information and documentation — Records management — Part 1: General
ISO/TR 15489-2, Information and documentation — Records management — Part 2: Guidelines
ISO/TS 23081-1, Information and documentation — Records management processes — Metadata for
records — Part 1: Principles
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3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 12651, ISO 15489-1 and
ISO/TR 15489-2 and the following apply.
3.1
authentic electronic document-based information
electronic document-based information the accuracy, reliability and integrity of which are maintained over time
3.2
document-based information
substantive information that can be treated as a unit (e.g. an image, text, spreadsheet, database views)
NOTE Document-based information is inclusive of, but not necessarily limited to: text, images, tabular data (e.g. a
spreadsheet), or any combination thereof.
3.3
document-based information content
substantive content contained in document-based information
3.4
document-based information context
information about the circumstances of electronic document-based information creation, control, use, storage
and management, and information about its relationship to other similar material
3.5
document-based information structure
logical and physical attributes of document-based information
NOTE Logical attributes consist of the logical order, e.g. a hierarchy with identifiable subparts, whereas physical
attributes comprise elements, e.g. type font, spacing.
3.6
electronic archiving
storage of electronic information in an independent physical or logical space where the information is
protected from loss, alteration and deterioration
NOTE The information may be used as reliable evidence in the future if it has been protected in this manner.
3.7
long-term preservation
period of time that electronic document-based information is maintained as accessible and authentic evidence
NOTE This period of time can range between a few years to hundreds of years, depending upon the needs and
requirements of the organization. For some organizations, this period of time would be determined by regulatory
compliance, legal requirements and business needs. For other oranizations, such as archival repositories holding public
records, the period of time required to retain electronic document-based information is usually thought to be hundreds of
years.
3.8
metadata
data describing the content (including indexing terms for retrieval), context and structure of electronic
document-based information and their management over time
3.9
migration
process of transferring electronic document-based information from one software/hardware environment or
storage medium to another environment or storage medium with little or no alteration of structure and no
alteration in content and context
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3.10
storage repository
storage repository organization or entity charged with the storage and maintenance of authentic electronic
document-based information
NOTE It is recognized that this definition is different from technical definitions of “storage repositories”.
3.11
technological obsolescence
displacement of an established technical solution in a marketplace as a result of major technological
developments or improvements
4 Symbols and abbreviated terms
ASCII American Standard Code for Information Interchange
CRC Cyclical Redundancy Code
HTML Hyper Text Markup Language
JPEG Joint Photographic Engineers Group
OCR Optical Character Recognition
PDF/A-1 Portable Document Format — Archive
SHA-1 Standard Hash Algorithm 1
TIFF Tagged Image File Format
WORM Write Once Read Many (times)
XML Extensible Markup Language
5 Long-term preservation
5.1 General
Increasingly, the proliferation of computer technologies that support the creation, use, storage and
maintenance of information, results in private and public sector organizations relying on electronic
document-based information as the official evidence of their business activities. Consequently, organizations
increasingly face the challenge of ensuring the long-term accessibility of authentic electronic information that
was created within reliable and trustworthy information systems and stored on electronic media that might be
subject to technological obsolescence that if left uncorrected will make the document-based information
irretrievable. The importance of this problem is compounded by the fact that organizations are increasingly
conducting activities and transactions where no paper evidence exists.
It is essential, therefore, that organizations develop and apply a well-defined strategy for providing long-term
preservation and retrieval of authentic electronic document-based information. Subclause 5.2 defines the
elements of such a strategy.
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5.2 Goals of a long-term preservation strategy
5.2.1 General
This subclause identifies six key issues that storage repositories should consider when they are developing a
long-term preservation strategy.
5.2.2 Readable electronic document-based information
A long-term preservation strategy should ensure that electronic document-based information remains
readable into the future. To achieve this, the bit stream comprising electronic document-based information
should be accessible on the computer system or device that:
⎯ initially created it or
⎯ currently stores it or
⎯ currently accesses it or
⎯ will be used to store the electronic information in the future.
These four processablity options are predicated on the fact that electronic document-based information stored
on digital storage media can become unreadable. There are two primary ways in which this can occur.
One is the result of exposure to hostile storage conditions. All of the media currently used for storing electronic
document-based information share a common vulnerability to poor environmental conditions, e.g. fluctuations
in temperature and humidity. These adverse conditions either damage the media or accelerate the ageing
process. Different types of digital storage media require different levels of controlled storage environment to
ensure maximum longevity. Some storage technologies are prone to data corruption through magnetic field
interference, dust and environmental contaminants (magnetic storage media), while others (optical storage
media) are not as prone to these outside factors and less susceptible to media damage outside tightly
controlled storage environments. Regardless of which storage technology is in use, it is important to recognize
that all forms of storage media can deteriorate and/or degrade through environmental changes.
The second is that non-readability may occur through media obsolescence, which occurs when a storage
device (e.g. a tape or disk) is physically incompatible with the available computer hardware (e.g. a tape or disk
drive) and therefore cannot be read. Based on past trends, media obsolescence in the future seems inevitable
because advances in storage technology continually introduce changes in the way the electronic
document-based information is physically stored (e.g. changes in recording technology, changes in disk drive
hardware/software interfaces), the form factor of the storage media and in the way the underlying bit stream of
document-based information is physically represented (e.g. error correction codes) or the form factor of the
storage media. Consequently, over time, older storage media will become incompatible with subsequently
used media.
A long-term preservation strategy should specifically address media obsolescence by establishing procedures
for periodically transferring document-based information from older to newer media.
NOTE Data readability is important along with data formatting. Ensuring that the data are formatted in a fashion
(i.e. technology neutral formats) that enables users in the future to process the data, should be taken into consideration.
5.2.3 Intelligible electronic document-based information
A long-term preservation strategy should provide intelligible electronic document-based information. Digital
information is only intelligible to a computer if the computer also has access to information describing how to
interpret the underlying bit stream. The intelligibility of electronic document-based information, therefore, is a
function of information about what the bit stream in fact represents and the processing software’s capacity to
take appropriate action based on this information.
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EXAMPLE The binary code (1s and 0s) comprising a digital Tagged Image File Formatted (TIFF) image carries no
intelligibility in its own right. Rather, the image’s file header, which contains information such as byte order and the
compression algorithm used, enables a computer (through a combination of its operating system and image software) to
display and print the image. Similarly, a word processing document carries metadata that makes it intelligible to word
processing software.
5.2.4 Identifiable electronic document-based information
A long-term preservation strategy should provide identifiable document-based information. Identifiable
document-based information should be organized, classified and described in such a way that it is possible for
users and information systems to distinguish between information objects based upon a unique attribute such
as name or ID number. Aggregating electronic document-based information into categories based upon
shared attributes can facilitate searching and retrieval. Failure to provide such identification can severely limit
searching and retrieval.
5.2.5 Retrievable document-based information
A long-term preservation strategy should provide retrievable document-based information, meaning that
discrete information objects (or parts of them) can be retrieved and displayed. Retrievability is typically
software-dependent in that it requires keys or pointers that link the logical structure of information objects (e.g.
data fields or text strings) to their physical storage location.
Generally, this linkage is found in a database record, file system directory structure, file allocation table,
header or label that includes the information required to locate the beginning of an object, to indicate the
number of bytes of each component or data element and to establish its physical location on the storage
medium.
The interpretation of the logical structure of document-based information is a function of an operating system
or device driver in conjunction with a particular application system developed to store, manage and access
digital information. The retrievability of information objects is therefore inextricably linked to a device driver,
software application, file system or operating system.
Newer generations of file formats that support the readability of older file formats help ensure the ability to
retrieve electronic document-based information. Backward compatibility however, can be limited because
many software vendors support only certain file formats, while others support all versions of various data
formats. An example of this would be support for TIFF, JPEG or HTML formatted data, which include
backward compatibility.
5.2.6 Understandable document-based information
A long-term preservation strategy should ensure that document-based information is understandable. In order
for electronic document-based information to be understandable, it should convey information to both
computers and humans. However, the meaning of discrete document-based information is not determined
solely by its content. Rather, meaning is derived from the context of both its creation and its use
(i.e. metadata). As such, storage repositories should be aware that ensuring the understandability of electronic
document-based information differs sharply from ensuring the understandability of paper documentation.
Unlike paper documentation, where their physical characteristics typically convey the context of its creation
and use, the context of creating and using electronic document-based information is usually linked logically
rather than physically.
EXAMPLE A series of paper documents regarding a particular transaction may be stapled together or placed in a file
folder, whereas electronic document-based information of a similar transaction may exist on multiple media in multiple
locations and therefore should be electronically tied together. These logical linkages can include identification of both the
business process that led to the transaction as well as the participants in the transaction.
The context of creation and use also involves relationships among other document-based information that has
been be captured in a variety of ways, including a reference code in a document profile to the other material
dealing with the same issue, or a classification code that links each instance of document-based information
relating to the same transaction.
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Successful retrieval of electronically stored document-based information therefore depends in part upon
preservation of these logical linkages regardless of the length of time they are retained.
5.2.7 Authentic electronic document-based information
5.2.7.1 General
A key goal of a long-term preservation strategy is to ensure the protection of authentic document-based
information. Authentic electronic document-based information is what it purports to be, i.e. reliable information
that over time has not been altered, changed or otherwise corrupted. Organizations seeking to provide
long-term access to document-based information that is authentic should consider three critical aspects in
their strategy:
a) transfer and custody;
b) the storage environment;
c) access and protection.
5.2.7.2 Document-based information transfer and custody
It is difficult to protect electronic document-based information from alteration, so long as it remains in a
production environment and is not stored on non-alterable, write-once media. Accordingly, a long-term
preservation strategy should provide for the transfer of document-based information from production
environments and from the originators and recipients to a storage system or storage repository, i.e. an
operationally independent third-party charged with maintaining document-based information according to
documented policies and practices.
5.2.7.3 Storage environment
A long-term preservation strategy should specify a stable storage environment for media containing electronic
document-based information because hostile or improperly controlled environments put the information at risk.
5.2.7.4 Document-based information access and protection
A long-term preservation strategy should provide mechanisms to restrict access to electronic document-based
information and protect it from deliberate or accidental alteration and corruption.
Electronic document-based information stored on rewritable media can be altered without leaving any physical
evidence. Electronic document-based information is also vulnerable to accidental corruption during a transfer
between media and information systems. As such, organizations seeking to ensure the authenticity of
electronic document-based information over time should establish appropriate policy, practice and
technology-based controls. Examples of common technology-based controls include:
⎯ use of WORM (i.e. non-rewritable) magnetic or optical media;
⎯ secure client-server architectures that can be used to block direct access to electronic document-based
information, with the net effect of providing “read-only” access;
⎯ Cyclical Redundancy Check code values (CRCs) commonly used as a technique for establishing the
reliability of electronic transmissions and are therefore, particularly useful for verifying that no changes
have been made to the electronic document-based information since being initially stored;
⎯ one-way hash functions (e.g. SHA-1) employing an algorithm that can compress electronic
document-based information into a fixed-length number of bits that effectively becomes a unique
"fingerprint" of the electronic document-based information, and can subsequently be used to demonstrate
it has not been altered.
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6 Elements of a long-term preservation strategy
6.1 General
Maintaining accurate, reliable and trustworthy electronic document-based information means ensuring the
following.
⎯ It can be read and correctly interpreted by a computer application.
⎯ It can be rendered in a format understandable to humans.
⎯ It has the logical and physical structure, substantive content and context that were apparent at the time of
creation or receipt.
Limited electronic media durability and inevitable technology obsolescence will force storage repositories,
charged with providing long-term preservation of authentic and processable electronic document-based
information, to make critical choices regarding long-term access. To deal with the challenges of media
durability and technology obsolescence, storage repositories will find it necessary to employ diverse strategies
and tools. These strategies and tools can be conceptually divided into three primary activities that collectively
form the foundation of any long-term preservation strategy.
a) First, storage repositories should undertake media renewal (see 6.2) to address media durability.
b) Second, where automated tools exist, document-based information migration (see 6.4) is a viable option
to address technology obsolescence by transferring document-based information from one technology
platform to another.
c) Third, when digital information and images are stored within legacy information systems where no
automated migration tools exist, a more robust approach may be required. The emulation of legacy
information systems within current technology environments may be required. Although this course of
action has a conceptual appeal, up to this point it has encountered operational resistance for the purpose
of long-term access to authentic electronic document-based information. Therefore, emulation is not
addressed further in this document.
6.2 Media renewal
6.2.1 General
Limited media durability and technology obsolescence suggest that periodic media renewal is both inevitable
and a base-line requirement for ensuring long-term preservation of authentic and processable electronic
documentation by keeping the original bit stream “alive”. Media renewal requires that electronic
document-based information be either reformatted or copied as detailed in 6.2.2 and 6.2.3
6.2.2 Reformatting electronic
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