1. Don Sawyer /NASA/NSSDC
ISO “Reference Model For an Open Archival Information System (OAIS)” Tutorial Presentation
Lou Reich /CSC
Don Sawyer /NASA/NSSDC
May 2000 1

2. Outline of Talk History Reference Model overview
Digital Archive Directions (DADs) workshop
AWIICS workshop
Reference Model Status

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. Getting Started First open US workshop held October 1995
Variety of government, academic, and industry participation, including National Archives
Active US working group was formed
US workgroup activities are fully open
New participants always welcome
Plans, minutes, drafts available from Web
Broad international workshops also held
Britain and France
Issue resolution at CCSDS international workshops

7. 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
Adopting terminology that crosses various disciplines
Traditional archivists
Scientific data centers
Digital libraries
Getting favorable comments wherever exposed

8. Reference Model for an Open Archival Information System

9. 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
Additional OAIS responsibilities are identified later and are more fully defined in the Reference Model document
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

10. Document Organization
Introduction
Purpose and Scope, Applicability, Rationale, Road Map for Future Work, Document Structure, and Definitions of Terms
OAIS Concepts
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
Migration perspectives
Media migration, compression, and format conversions
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

11. 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

12. Model View of an OAIS’s 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

13. OAIS Information Definition
Information is defined as any type of knowledge that can be exchanged, and this information is always expressed (i.e., represented) by some type of data
In general, it can be said that “Data interpreted using its Representation Information yields Information”
In order for this Information Object to be successfully preserved, it is critical for an archive to clearly identify and understand the Data Object and its associated Representation Information
Interpreted
Using its
Yields
Data
Object
Representation
Information
Information
Object

14. Information Package Definition
Preservation
Description
Information
Content
Information
An Information Package is a conceptual container of two types of information called Content Information and Preservation Description Information (PDI)

15. 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

16. External Data Flow Diagram
Producer
Submission
Information
Packages
OAIS
Archival
Information
Packages
Legend
= Entity
Information
Package
Data Object
= Data Flow =
queries
This diagram concentrates on the flow of information among producer, Consumers and the OAIS, and does not include flows that involve management
query
response
Dissemination
Information
Packages
orders
Consumer 8

17. OAIS Responsibilities
Negotiates and accepts Information Packages 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

18. Detailed Models
Overview

19. 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

20. Detailed Models
Information Model

21. 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 variant of Object Modeling Technique (OMT) as a notation (being updated to UML)

22. OMT Notation Overview Class: Multiplicity of Associations:
Class Name
Class
Exactly one
Class
Many (zero or more)
Aggregation:
Assembly Class
Class
Optional (zero or one) 1+
Class
One or more
Part -1 Class
Part-2 Class
Specialization:
Association:
Association Name
Parent Class
Class-1
Class-2
Child -1 Class
Child-2 Class

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

24. Representation Information
The Representation Information accompanying a physical object like a moon rock may give additional meaning, as a result of some analysis, to 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

25. Recursive Nature of Representation Information
Preexisting standards that define primitive data-types
Mapping rules that map those primitive data-type into the more complex data-type concept used by the Data Object
Other semantic informa-tion that aids in the under-standing of the Data such as a Data Dictionary

26. Sample Representation Net

27. Types of Information Used in OAIS

28. 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)

29. 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

30. Example of Preservation Description Information
Content Information Type
Reference
Provenance
Context
Fixity
Space Science Data
Bibliographic Information
Software Package
Object Identifier
Journal Reference
Mission, instrument, and title attribute set
ISBN
Title
Author
Name
Version number
Serial Number
Instrument Description
Processing History
Sensor Description Instrument
Instrument mode
Decommutation map
Software Interface Specifications
Printing history
Copyright
Position in series
Manuscripts
References
Revision Histroy
License holder
Registration
Calibration history
Related data sets
Mission
Funding history
Related References
Dewy Decimal System
Publishing Data
Publisher
Help file
User Guide
Related Software
Language
CRC
Checksum
Reed-Solomon coding
Author Digital signature
Cover
Certificate
Encryption

31. 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.

32. 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

33. OAIS Archival Information Package
Package (AIP)
Packaging
Information
Package
Descriptor
derived from
delimited by
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
The AIP is a basic concept in the OAIS. The AIP contains a piece of
information that the OAIS has to be preserve.
The AIP isq defined to be composed of two types of information
objects : one is called the Content Information (CI) and the other is
called the Preservation Description Information (PDI) (terminology
under discussion)
The purpose in making this distinction is to propote a clear difference
between that information (the CI) that is the primary focus of
archival preservation and that information which is needed to support
the long term preservation or the primary information.
The AIP is a generic term, it will be specialised in AIC
(Archiving Information Collection) and AIU (Archiving Information Unit)
e.g., • Hardcopy document
• Document as an electronic
file together with its format
description
• Scientific data set consisting
of images and text in three
electronic files together with
format descriptions
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 9

34. 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

35. 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

36. 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

37. Detailed Models
Functional View

38. 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

39. 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

40. OAIS Functional Entities
Descriptive
Info.
Data
Management
Descriptive
Info.
Requests P R O D U C E C O N S U M E R
Ingest
other
information
Access
SIP
AIP
AIP
DIP
Archival
Storage
Administration
We can see, in this view, that the AIP is a specialized object create from a more genenal object called ‘Information package’
MANAGEMENT
SIP = Submission Information Package
AIP = Archival Information Package
DIP = Dissemination Information Package 10

41. 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
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

42. Ingest Functions
Schedule Submission Delivery: negotiates a data submission schedule with the producer
Receive Submission: provides the appropriate storage capability or devices to receive a SIP from the producer. The Receive SIP function may represent a legal transfer of custody for the CI in the SIP, and may require that special access controls be placed on the contents
Generate Archival Information Package: transforms one or more SIPs into one or more AIPs that conforms to the internal data model of the archive.
Generate Descriptive Information: extracts Descriptive Information from the AIPs to populate the data management system.
Coordinate Updates: responsible for transferring the AIPs to Archival Storage and the Descriptive Information to Data Management

43. Ingest Data Flow Diagram

44. Analysis of Archive Issues Using OAIS RM
Migration

45. 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

46. 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

47. 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

48. Analysis of Archive Issues Using OAIS RM
Archive Associations

49. 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

50. 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

51. 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)

52. 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.

53. 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

54. Reference Model Acceptance
Reference model has been getting good reviews
Society of American Archivists 1997 annual meeting
NAGARA 1998 Annual Meeting
Various international conferences
Major context for June 1998 Digital Archive Directions (DADs) workshop hosted by NARA
Framework for October 1999 Archival Workshop on Ingest, Identification, and Certification (AWIICS) hosted by NARA

55. DADs Workshop Recommendations
Working groups identified several ‘best practices’ and standards desired, including:
Recommended data ingest methodology
Best practices for digitizing analogue data
Best practices for media selection, testing and usage
Best practices for error control through the archive
Archival Submission Information Package standard
Consumer Archive Interface standard
Unique Archival Information Package Identifier standard
AIP Content Layered Model and Standard APIs report
Plenary recommended a coordination function be established
Promote the reference model
Promote coordination of work on best practices and standards
Promote development of an archive accreditation method

56. AWIICS Conclusions
A diverse community of science data centers, libraries, electronic records and traditional archives sees the benefit, and is willing to participate, in developing standards in the following areas:
Ingest Methodology for producer interactions with the archive
Certification of digital archives and preservation methodology
Access scenarios and derived requirements for identification of, and access to, archived information

57. Reference Model Status
Ultimate success of OAIS Reference Model effort depends on obtaining adequate review and comment
CCSDS Reference Model Red Book released August 1999
ISO Draft International Standard (DIS) expected May 2000
Same content as CCSDS Red Book
Held up by ISO TC20 secretariat backlog
Comments are actively solicited
Participate in various ways:
ISO TC20/SC 13 review in your country
CCSDS review by your space agency
Send comments to
All comments will be considered and non-editorial comments will get a response