1. 10041267M-1 ISO “Reference Model For an Open Archival Information System (OAIS)” ISO “Reference Model For an Open Archival Information System (OAIS)” Tutorial Presentation Don Sawyer /NASA/NSSDC Lou Reich /CSC October 2002

2. 10041267M-2 Outline of Talk History Reference Model overview Some Applications Follow-on Activities

3. 10041267M-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. 10041267M-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. 10041267M-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. 10041267M-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. 10041267M-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 e-mail comments/critiques Broad international workshops also held — UK and France — Issue resolution at ISO/Consultative Committee for Space Data Systems international workshops

8. 10041267M-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. 10041267M-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. 10041267M-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: — http://www.ccsds.org/documents/pdf/CCSDS-650.0-B-1.pdf

11. 10041267M-11 Reference Model for an Open Archival Information System Technical Overview

12. 10041267M-12 Open Archival Information System (OAIS) Open –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

13. 10041267M-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

14. 10041267M-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. 10041267M-15 Model View of an OAIS Environment OAIS (archive) Management Producer Consumer 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

16. 10041267M-16 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 OAIS Responsibilities

17. 10041267M-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 Data Object Interpreted Using its Representation Information Yields Information Object

18. 10041267M-18 Information Package Definition An Information Package is a conceptual container holding two types of information – Content Information – Preservation Description Information (PDI) Preservation Description Information Content Information

19. 10041267M-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. 10041267M-20 External Data Flow View Producer Consumer queries result sets orders OAIS Archival Information Packages Submission Information Packages Dissemination Information Packages

21. 10041267M-21 Detailed Models Overview

22. 10041267M-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. 10041267M-23 Detailed Models Information Model

24. 10041267M-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. 10041267M-25 UML Notation

26. 10041267M-26 Information Objects Information Object Representation Information 1+ interpreted using 1+ Data Object interpreted using Physical Object Digital Object Bit Sequence 1+

27. 10041267M-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. 10041267M-28 Recursive Nature of Representation Information Structure Information Semantic Information Other Representation Information

29. 10041267M-29 Types of Information Used in OAIS

30. 10041267M-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. 10041267M-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. 10041267M-32 Preservation Description Information

33. 10041267M-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. 10041267M-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. 10041267M-35 OAIS Archival Information Package Archival Information Package (AIP) Content Information Preservation Description Information (PDI) 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 Packaging Information Package Description further described by delimited by derived from e.g., How to find Content information and PDI on some medium e.g., Information supporting customer searches for AIP

36. 10041267M-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. 10041267M-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. 10041267M-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. 10041267M-39 Detailed Models Functional View

40. 10041267M-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. 10041267M-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. 10041267M-42 OAIS Functional Entities SIP = Submission Information Package AIP = Archival Information Package DIP = Dissemination Information Package SIP Descriptive Info. AIP DIP Administration PRODUCERPRODUCER CONSUMERCONSUMER queries result sets MANAGEMENT Ingest Access Data Management Archival Storage Descriptive Info. Preservation Planning orders

43. 10041267M-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. 10041267M-44 Ingest Data Flow Diagram

45. 10041267M-45 Preservation Planning

46. 10041267M-46 Preservation Perspectives

47. 10041267M-47 Migration Context

48. 10041267M-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. 10041267M-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. 10041267M-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. 10041267M-51 Archive Interoperability

52. 10041267M-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. 10041267M-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. 10041267M-54 Federated Archives Local Consumer Local Consumer Global Consumer Dissemination Information Package (Optional) Dissemination Information Package (Optional) Administration Common Catalog Access IngestAccess OAIS 1 Administration IngestAccess OAIS 2 Administration

55. 10041267M-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. 10041267M-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. 10041267M-57 Some Applications

58. 10041267M-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. 10041267M-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. 10041267M-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. http://www.aristote.asso.fr/ (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. 10041267M-61 Follow-on Activities Research Libraries Group has established a web page to track OAIS implementation efforts and issues — http://www.rlg.org/longterm/oais.html 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