1. Don Sawyer /NASA/NSSDC
ISO “Reference Model For an Open Archival Information System (OAIS)” Tutorial Presentation
Don Sawyer /NASA/NSSDC
Lou Reich /CSC
October 2002 1

2. Outline of Talk History Reference Model overview Some Applications
Follow-on Activities

3. NASA Role National Space Science Data Center
NASA’s first digital archive
Experienced many technology changes since 1966
Consultative Committee for Space Data Systems
International group of space agencies
Developed variety of science discipline- independent standards
Became working body for an ISO TC 20/ SC 13 about 1990
TC20: Aircraft and Space Vehicles
SC13: Space Data and Information Transfer Systems

4. Initial Archive Standards Proposal
ISO suggested that SC 13 should develop archive standards
Address data used in conjunction with space missions
Address intermediate and indefinite long term storage of digital data

5. Response
Response to Consultative Committee for Space Data Systems (CCSDS) and ISO TC 20/SC 13
No framework widely recognized for developing specific digital archive standards
Begin by developing a ‘Reference Model’ to establish common terms and concepts
Ensure broad participation, including traditional archives
(Not restricted to space communities; all participation is welcome!)
Focus on data in electronic forms, but recognize that other forms exist in most archives
Follow up with additional archive standards efforts as appropriate

6. What is a Reference Model?
A framework
for understanding significant relationships among the entities of some environment, and
for the development of consistent standards or specifications supporting that environment.
A reference model
is based on a small number of unifying concepts
is an abstraction of the key concepts, their relationships, and their interfaces both to each other and to the external environment
may be used as a basis for education and explaining standards to a non-specialist.

7. Organizational Approach
Organize US contribution under a framework with NASA lead
Establish liaison with Federal Geographic Data Committee (FGDC) and National Archives and Records Administration (NARA)
Agency archives and users must be represented in this process
An “Open” process
Important to stimulate dialogue with broad archive/user communities
Results of US and International workshops put on WEB
Support comments/critiques
Broad international workshops also held
UK and France
Issue resolution at ISO/Consultative Committee for Space Data Systems international workshops
Broad US participation is viewed as essential
Can not be viewed as a “NASA show”
NISO is creditable with private and academic communities
FGDC has a federal role by executive order

8. Technical Approach Investigate other Reference Models.
ISO “Seven Layer”Communications Reference Model
ISO Reference Model for Open Distributed Processing
ISO TC211 Reference Model for Geomantics
Define what is meant by ‘archiving of data’
Break ‘archiving’ into a few functional areas (e.g., ingest, storage, access, and preservation planning)
Define a set of interfaces between the functional areas
Define a set of data classes for use in Archiving
Choose formal specification techniques
Data flow diagrams for functional models and interfaces
Unified Modeling Language (UML) for data classes

9. Results Reference Model targeted to several categories of reader
Archive designers
Archive users
Archive managers, to clarify digital preservation issues and assist in securing appropriate resources
Standards developers
Adopted terminology that crosses various disciplines
Traditional archivists
Scientific data centers
Digital libraries

10. Reference Model Status
Already widely adopted as starting point in digital preservation efforts
Digital libraries (e.g., Netherlands National Library)
Traditional archives (e.g., US National Archives)
Scientific data centers (e.g., National Space Science Data Center)
Commercial Organizations (e.g., Aerospace Industries Association preservation working team)
Recently approved for publication as final CCSDS and ISO (14721:2002) standards
CCSDS version is available at:

11. Reference Model for an Open Archival Information System Technical Overview

12. Open Archival Information System (OAIS)
Reference Model standard(s) are developed using a public process and are freely available
Information
Any type of knowledge that can be exchanged
Independent of the forms (i.e., physical or digital) used to represent the information
Data are the representation forms of information
Archival Information System
Hardware, software, and people who are responsible for the acquisition, preservation and dissemination of the information
This reference model is called : Reference Model for an OAIS
(Open Archival Information System)
These tems have to be explained :
In the framework of the archiving reference model elaboration,
a glossary has been defined. This is a crucial point for the common
understandding of archival concepts 4

13. Document Organization
Introduction
Purpose and Scope, Applicability, Rationale, Road Map for Future Work, Document Structure, and Definitions of Terms
OAIS Concepts and Responsibilities
High level view of OAIS functionality and information models
OAIS external environment
Minimum responsibilities to become an “OAIS”
Detailed Models
Functional model descriptions and information model perspectives
Preservation perspectives
Media migration, compression, format conversions, and access service preservation
Archive Interoperability
Criteria to distinguish types of cooperation among archives
Annexes
Scenarios of existing archives, compatibility with other standards
The current version ot the Reference model document is organised
as follow
The parts in blue will no detailed to day 6

14. Purpose, Scope, and Applicability
Framework for understanding and applying concepts needed for long-term digital information preservation
Long-term is long enough to be concerned about changing technologies
Starting point for model addressing non-digital information
Provides set of minimal responsibilities to distinguish an OAIS from other uses of ‘archive’
Framework for comparing architectures and operations of existing and future archives
Basis for development of additional related standards
Addresses a full range of archival functions
Applicable to all long-term archives and those organizations and individuals dealing with information that may need long-term preservation
Does NOT specify any implementation

15. Model View of an OAIS Environment
Producer is the role played by those persons, or client systems, who provide the information to be preserved
Management is the role played by those who set overall OAIS policy as one component in a broader policy domain
Consumer is the role played by those persons, or client systems, who interact with OAIS services to find and acquire preserved information of interest
The environment surrounding the OAIS is given by this simple model
outside the OAIS are :
producers : play the rôle of those who provide the information to preserve
management : play the rôle of those who set overall OAIS policy
consumers : play the rôle of those who interact with the OAIS services to find information of interest and to access this information
OAIS
(archive)
Producer
Consumer
Management 7

16. OAIS Responsibilities
Negotiates and accepts Information from information producers
Obtains sufficient control to ensure long-term preservation
Determines which communities (designated) need to be able to understand the preserved information
Ensures the information to be preserved is independently understandable to the Designated Communities
Follows documented policies and procedures which ensure the information is preserved against all reasonable contingencies
Makes the preserved information available to the Designated Communities in forms understandable to those communities 11

17. OAIS Information Definition
Information is always expressed (i.e., represented) by some type of data
Data interpreted using its Representation Information yields Information
Information Object preservation requires clear identification and understanding of the Data Object and its associated Representation Information
Interpreted
Using its
Yields
Data
Object
Representation
Information
Information
Object

18. Information Package Definition
Preservation
Description
Information
Content
Information
An Information Package is a conceptual container holding two types of information
Content Information
Preservation Description Information (PDI)

19. Information Package Variants
Submission Information Package
Negotiated between Producer and OAIS
Sent to OAIS by a Producer
Archival Information Package
Information Package used for preservation
Includes complete set of Preservation Description Information for the Content Information
Dissemination Information Package
Includes part or all of one or more Archival Information Packages
Sent to a Consumer by the OAIS

20. External Data Flow View
Producer
Submission
Information
Packages
OAIS
Archival
Information
Packages
queries
result
sets
orders
Dissemination
Information
Packages
Consumer

21. Detailed Models
Overview

22. Overview of Detailed Models
It was decided to do both a functional and an information model of the OAIS
Both models were tasked to:
Use the models to better communicate OAIS Concepts
Use a well established, formal modeling technique
Stay as implementation independent as possible
Avoid detailed designs

23. Detailed Models
Information Model

24. General Principles
Define classes of “information objects’ that illustrate information necessary to enable Long-term storage and access to Archives
The class definition should be implementation Independent
Use a subset of Unified Modeling Language (UML)

25. UML Notation

26. Information Objects Information Object Representation 1+ interpreted
using
Data
Physical
Digital
Bit
Sequence

27. Representation Information
The Representation Information accompanying a physical object, like a moon rock, may give additional meaning
It typically is a result of some analysis of the physically observable attributes of the rock
The Representation Information accompanying a digital object, or sequence of bits, is used to provide additional meaning.
It typically maps the bits into commonly recognized data types such as character, integer, and real and into groups of these data types.
It associates these with higher level meanings which can have complex inter-relationships that are also described

28. Recursive Nature of Representation Information
Structure Information
Semantic Information
Other Representation Information

29. Types of Information Used in OAIS

30. Content Information
The information which is the primary object of preservation
An instance of Content Information is the information that an archive is tasked to preserve.
Deciding what is the Content Information may not be obvious and may need to be negotiated with the Producer
The Data Object in the Content Information may be either a Digital Object or a Physical Object (e.g., a physical sample, microfilm)

31. Preservation Description Information
Provenance Information
Describes the source of Content Information, who has had custody of it, what is its history
Context Information
Describes how the Content Information relates to other information outside the Information Package
Reference Information
Provides one or more identifiers, or systems of identifiers, by which the Content Information may be uniquely identified
Fixity Information
Protects the Content Information from undocumented alteration

32. Preservation Description Information

33. Descriptive Information
Contain the data that serves as the input to documents or applications called Access Aids.
Access Aids can be used by a consumer to locate, analyze, retrieve, or order information from the OAIS.

34. Packaging Information
Information which, either actually or logically, binds and relates the components of the package into an identifiable entity on specific media
Examples of Packaging Information include tape marks, directory structures and filenames

35. OAIS Archival Information Package
Package (AIP)
Package
Description
derived from
delimited by
Packaging
Information
e.g., Information
supporting customer
searches for AIP
e.g., How to find Content
information and PDI on
some medium
Preservation
Description
Information
(PDI)
Content
Information
further described by
e.g., • Hardcopy document
• Document as an electronic
file together with its format
description
• Scientific data set consisting
of image file, text file,
and format descriptions file
describing the other files
e.g., • How the Content Information came
into being, who has held it, how it
relates to other information, and how
its integrity is assured

36. AIP Types Based on the difference in Content Object complexity
AIUs contain a single Data Object as the Content Object
AICs contain multiple AIPs in their Content Objects
Each member of an AIC is an AIP containing Content Information and PDI
The AIC contains unique PDI on the collection process

37. Package Descriptors and Access Aids
Package descriptors are needed by an OAIS to provide visibility and access to the OAIS holdings
Package Descriptors contain 1 or more Associated Descriptions which describe the AIP Content Information from the point of view of a single Access Aid
Some example of Access Aids Include:
Finding Aids - assist the consumer in locating information of interest
Ordering Aids - allow the consumer to discover the cost of and order AIUs of interest
Retrieval Aids - enable authorized users to retrieve the AIU described by the Unit Descriptor from Archival Storage

38. Information Model Summary
Presented a model of information objects as containing data objects and representation objects
Classified information required for Long-term archiving into 4 classes: Content Information, PDI, Packaging Information and Descriptive Information
Described how these classes would be aggregated and related in an AIP to fully describe an instance of Content Information
Presented information needed for Access, in addition to that needed for Long-term Preservation
Put the Access oriented structures in the context of the other data needed to operate an OAIS

39. Detailed Models
Functional View

40. General Principles
Highlight the major functional areas important to digital archiving
Use functional decomposition to clarify the range of functionality that might be encountered
Don't decompose beyond two levels to avoid becoming too implementation dependent
Provide a useful set of terms and concepts
Do not imply that all archives need to implement all the sub-functions
Identify some common services which are likely to be needed, and are assumed to be available, as underlying support

41. Common Services
Modern, distributed computing applications assume a number of supporting services
Examples of Common Services include:
inter-process communication
name services
temporary storage allocation
exception handling
security
file and directory services

42. OAIS Functional Entities
Preservation Planning P R O D U C E C O N S U M E R
Descriptive
Info.
Data
Management
Descriptive
Info.
queries
result sets
Ingest
Access
orders
SIP
DIP
AIP
Archival
Storage
AIP
Administration
MANAGEMENT
SIP = Submission Information Package
AIP = Archival Information Package
DIP = Dissemination Information Package

43. Functional Entities In An OAIS
Ingest: This entity provides the services and functions to accept Submission Information Packages (SIPs) from Producers and prepare the contents for storage and management within the archive
Archival Storage: This entity provides the services and functions for the storage, maintenance and retrieval of Archival Information Packages
Data Management: This entity provides the services and functions for populating, maintaining, and accessing both descriptive information which identifies and documents archive holdings and internal archive administrative data.
Administration: This entity manages the overall operation of the archive system
Preservation Planning: This entity monitors the environment of the OAIS and provides recommendations to ensure that the information stored in the OAIS remain accessible to the Designated User Community over the long term even if the original computing environment becomes obsolete.
Access: This entity supports consumers in determining the existence, description, location and availability of information stored in the OAIS and allowing consumers to request and receive information products

44. Ingest Data Flow Diagram

45. Preservation Planning

46. Preservation Perspectives

47. Migration Context

48. Digital Migration
Digital Migration is defined to be the transfer of digital information, while intending to preserve it, within the OAIS.
Focus on preservation of the full information content
New information implementation replaces the old
OAIS has full control and responsibility over all aspects of the transfer
Three major motivators are seen to drive Digital Migrations of Archival Information Packages within an OAIS:
Media Decay
Increased Cost Effectiveness
New Consumer Service Requirements

49. Digital Migration Approaches
Four primary types of digital migration in response to motivators, ordered by increasing risk of information loss:
Refreshment
Media replacement with no bit changes
Replication
No change to Packaging Information or Content Information bits
Repackaging
Some bit changes in Packaging Information
Transformation
Reversible: Bit changes in Content Information are reversible by an algorithm
Non-reversible: Bit changes in Content Information are not reversible by an algorithm

50. Access Preservation
Effective access to digital information requires the use of software
Application Programming Interfaces (APIs) may be cost-effectively maintained across time by an OAIS when:
API is not too complex
API is applicable to a wide variety of AIUs
API source code may be ported to new environments
Extensive testing is needed to ensure against information loss
Preservation of executables by full emulation of underlying hardware is problematic
Hard to know what is the information being preserved
May not be possible to fully emulate associated devices

51. Archive Interoperability

52. Archive Interoperability Motivators
Users of multiple OAIS archives have reasons to wish for some interoperability or cooperation among the OAISs.
Consumers
Common finding aids to aid in locating information over several OAIS archives
Common Package Descriptor schema for access
Common DIP schema for dissemination, or a single global access site.
Producers
common SIP schema for submission to different archives
a single depository for all their products.
Managers
Cost reduction through sharing of expensive hardware increasing the uniformity and quality of user interactions with the OAIS

53. Categories of Archive Interactions
Independent: no knowledge by one OAIS of Standards implemented at another
Cooperating: Potentially common submission standards, and common dissemination standards, but no common access. One archive may make subscription requests for key data at the cooperating archive
Federated: Access to all federated OAIS is provided through a common set of access aids that provide visibility into all participating OAISs. Global dissemination and Ingest are options
Shared resources: An OAIS in which Management has entered into agreements with other OAISs is to share resources to reduce cost. This requires various standards internal to the archive (such as ingest-storage and access-storage interface standards), but does not alter the community’s view of the archive

54. Federated Archives Local Consumer Global OAIS 1 Consumer
Dissemination Information Package
(Optional)
Ingest
Access
OAIS 1
Administration
Access
Access
Global
Consumer
Common Catalog
Administration
Administration
OAIS 2
Ingest
Access
Access
Local
Consumer
Dissemination Information Package
(Optional)

55. Levels of Autonomy in Associated Archives
No interactions and therefore no association
Associations that maintain your autonomy. You have to do certain things to participate, but you can leave the association without notice or impact to you.
Associations that bind you by contract. To change the nature of this association you will have to re-negotiate the contract. The amount of autonomy retained depends on how difficult it is to negotiate the changes.

56. Reference Model Summary
Reference model is to be applicable to all digital archives, and their Producers and Consumers
Identifies a minimum set of responsibilities for an archive to claim it is an OAIS
Establishes common terms and concepts for comparing implementations, but does not specify an implementation
Provides detailed models of both archival functions and archival information
Discusses OAIS information migration and interoperability among OAISs

57. Some Applications

58. Basis of Systems Architectures
NEDLIB (Networked European Deposit Library) effort used OAIS Reference Model as a basis for the design and architecture of Deposit System for Electronic Publications (DSEP)
National Library of Australia used it as basis for their implementation
CEDARS: A multi-site UK project to create exemplars in Digital Archiving is using OAIS representation data as the basis for research into long term preservation
NSSDC (National Space Science Data Center ) is evolving their archive using OAIS RM as a basis for a new architecture
SIPAD: French space agency plasma physics archive used the OAIS as a basis for design
METS (Metadata Encoding and Transmission Standard) is using OAIS concepts in an implementation of types of Submission, Archival, and Dissemination Information Packages.
InterPARES, a body of National Archives from many countries, adopted OAIS as a starting point for their modeling work

59. Enhanced Communications and Productivity among varied Communities
National Archives and Records Administration contracted some work on long term preservation of collections to the San Diego Super Computer Center. Both parties claimed use of the OAIS RM saved several weeks of effort in the specification of the task
Similar experiences between:
National Library of France and French space agency (CNES) representatives
National Center for Supercomputer Applications HDF format developers and DNA researchers
Life Sciences Archive developer and micro-gravity researchers
United States Department of Agriculture and digital preservation experts

60. More OAIS Accomplishments
Royal Library of the Netherlands (RLN)
OAIS mandated in their implementation RFP
IBM implementing OAIS-based system for RLN (£5M project)
British National Library is following suit
France setting up a working group within ARISTOTE
interested in archive of digital information, including libraries and Dept of Justice.
(in french)
“astonishing unifying role” from OAIS reference model
OAIS likely to be used by CODATA archive task group in study on long-term preservation
Playing significant role in Research Libraries Group and OCLC (Online Computer Library Center) digital preservation work

61. Follow-on Activities
Research Libraries Group has established a web page to track OAIS implementation efforts and issues
CCSDS/ISO Producer-Archive Interface Methodology Standard
Provides framework for Producer/Archive interactions
Identifies steps and types of information exchanged during the ‘negotiation’
May be used as a checklist by archives
CCSDS Certification Coordination Function
Will track and summarize various archive certification efforts
Will attempt to extract high-level model/checklist
RLG is organizing a group to establish certification approaches