Introduction to the Reference Model for an Open Archival Information System (OAIS)

http://www.ukoln.ac.uk/

Introduction to the Reference Model for an Open Archival Information System (OAIS)

Michael Day,Digital Curation CentreUKOLN, University of [email protected]

Archives and Records Management, HIST 564 Applied Communication and IT Skills, University of Liverpool, 3 December 2007


University of Liverpool, 3 December 2007

Session outline

• Introduction to the OAIS Model:

– Background

– Mandatory Responsibilities

– Functional Model (repository view)

– Information Model (object view)

• Main application areas:

– Trusted repositories (compliance)

– The analysis and comparison of repositories

– Informing system design

– Preservation metadata



OAIS background (1)

• Reference Model for an Open Archival Information System (OAIS)

• Development led by the Consultative Committee for Space Data Systems (CCSDS)

• Issued as CCSDS Recommendation (Blue Book) 650.0-B-1 (January 2002)

• Also adopted as: ISO 14721:2003• Periodic reviews (no major changes from most

recent review)• http://public.ccsds.org/publications/archive/

650x0b1.pdf



OAIS background (2)

• OAIS is a reference model– This is fundamental to knowing how the

standard should be understood– The models provide a conceptual space for

informing the development of repository systems (and components), both technical and non-technical - implementation independent

– Some key concepts (e.g., Representation Information, Designated Community) have become fundamentally important in digital preservation discussions



OAIS purpose and scope (1)

• To define an Open Archival Information System – The term 'open' means that the document was

developed in an open way, and does not imply that access to an OAIS should be unrestricted

– An archive is defined as an "organization that intends to preserve information for access and use by a designated community." (p. 1-8)




• While an OAIS itself need not be permanent, the information being maintained has been deemed to need "Long Term Preservation"– Long term = long enough for there to be a

concern about the impact of changing technologies




• Primary focus on digital information• Specific aims include:

– A framework for the understanding and awareness of the archival concepts needed for long term preservation (access)

– Terminology and concepts for describing and comparing:

• Architectures and operations• Preservation strategies and techniques• Data models




• Specific aims (continued):– Consensus on elements and processes for long

term preservation– A foundation for other standards

• Applicability:– Applicable to any archive, but mainly focused

on organisations with responsibility for making information available for the long term

– Also of interest to those who create information




• Conformance:– An OAIS must support the information model -

but does not specify any particular method of implementation

– Mandatory responsibilities (section 3.1)– Caveats (section 1.4):

• "It is assumed that implementers will use this reference model as a guide while developing a specific implementation to provide identified services and content"




– Caveats (continued):• The model does not assume or endorse any

specific computing platform, system environment, system design paradigm, database management system, data definition language, etc.

– An OAIS may provide additional services – A conceptual framework to discuss and

compare archives• Road map for related standards (section 1.5)



OAIS definitions (1)

• OAIS - "An archive, consisting of an organization of people and systems, that has accepted the responsibility to preserve information and make it available for a Designated Community”

• Designated Community - the community of stakeholders and users that the OAIS serves

• Knowledge Base - a set of information, incorporated by a user or system, that allows that user or system to understand the received information




• Information Object - Data Object + Representation Information

• Representation Information - any information required to render, interpret and understand digital data

• Information Package - Conceptual linking of Content Information + Preservation Description Information + Packaging Information (Submission, Archival and Dissemination Information Packages)




• Preservation Description Information - information (metadata) about Provenance, Context, Reference, Fixity



OAIS high-level concepts (1)

• A summary of key high-level concepts that are formally modelled in section 4

• Defines: – The environment of an OAIS

• Producers, Consumers, Management• Recognises that an OAIS exists within a

wider context




– Definitions of information, Information Objects and their relationship with Data Objects

• Recognises the importance of a organisation's Knowledge Base in being able to understand information

• Introduces the Representation Information concept




– Definitions of Information Packages, conceptual containers of Content Information and Preservation Description Information

• The packaging of content is useful to support the submission of information to an OAIS or dissemination of information to Consumers

• Packaging Information encapsulates Content Information and Preservation Description Information, is discoverable by virtue of Descriptive Information (Figure 2-3)




Information Package Concepts and Relationships (Figure 2-3)




– Defines Preservation Description Information– Introduces Information Package variants

• Variants are:– Submission Information Package (SIP)– Archival Information Package (AIP)– Dissemination Information Package (DIP)

• Recognises that packages will need to vary depending upon their role



OAIS external interactions

• High level view of the interactions in an OAIS environment– Management interaction

• Charter and scope, Funding, Conflict resolution

– Producer interaction• Submission agreements

– Consumer interaction• Help desk questions, catalogue searches,

ordering of information



OAIS mandatory responsibilities (1)

• Negotiate for and accept appropriate information from information Producers

• Obtain sufficient control of the information provided to the level needed to ensure Long-Term Preservation

• Determine, either by itself or in conjunction with other parties, which communities should become the Designated Community and, therefore, should be able to understand the information provided



OAIS mandatory responsibilities (2)

• Ensure that the information to be preserved is Independently Understandable to the Designated Community. In other words, the community should be able to understand the information without needing the assistance of the experts who produced the information

• Follow documented policies and procedures which ensure that the information is preserved against all reasonable contingencies, and which enable the information to be disseminated as authenticated copies of the original, or as traceable to the original

• Make the preserved information available to the Designated Community



OAIS Functional Model (1)

• Six entities– Ingest– Archival Storage– Data Management– Administration– Preservation Planning– Access

• Described using UML diagrams ...



OAIS Functional Model (2)

4-1.

2

MANAGEMENT

Ingest

Data Management

SIP

AIPDIP

queries

result setsAccess

PRODUCER

CONSUMER

Descriptive Info

AIP

orders

Descriptive Info

Archival Storage

Administration

Preservation Planning

OAIS Functional Entities (Figure 4-1)



OAIS Functional Entities (1)

• Ingest - services and functions that accept SIPs from Producers; prepares AIPs for storage, and ensures that AIPs and their supporting Descriptive Information become established within the OAIS

• Archival Storage - services and functions used for the storage and retrieval of AIPs



Functions of Archival Storage




• Data Management -services and functions for populating, maintaining, and accessing a wide variety of information

• Administration - services and functions needed to control the operation of the other OAIS functional entities on a day-to-day basis

• Preservation Planning - services and functions for monitoring the OAIS environment and ensuring that content remains accessible to the Designated Community



Preservation Planning Functions




• Access - services and functions which make the archival information holdings and related services visible to Consumers



OAIS Information Objects (1)

• Information Object (basic concept):– Data Object (bit-stream)– Representation Information (permits “the full

interpretation of Data Object into meaningful information”)

• Information Object Classes:– Content Information– Preservation Description Information (PDI)– Packaging Information– Descriptive Information



OAIS Information Objects (2)Information

Object

RepresentationInformation

1+

interpretedusing1+Data

Object

interpretedusing

PhysicalObject

DigitalObject

BitSequence

1+

OAIS Information Object (Figure 4-10)




• Representation Information:– Any information required to render, interpret

and understand digital data (includes file formats, software, algorithms, standards, semantic information etc.)

– Representation Information is recursive in nature

– Essential that Representation Information itself is curated and preserved to maintain access to (render and interpret) digital data

• e.g. Format registries (GDFR, TNA's PRONOM-DROID)




Interpreted using

Semantic information

Structure Information

Other Representation

Informationadds meaning to

Representation Information

*

1

*

1

4-11

.1OAIS Representation Information Object (Figure 4-11)



OAIS Information Packages (1)

• Information package:– Container that encapsulates Content

Information and PDI– Packages for submission (SIP), archival

storage (AIP) and dissemination (DIP)– AIP = “... a concise way of referring to a set of

information that has, in principle, all of the qualities needed for permanent, or indefinite, Long Term Preservation of a designated Information Object”




• Archival Information Package (AIP):– Content Information

• Original target of preservation• Information Object (Data Object &

Representation Information)– Preservation Description Information (PDI)

• Other information (metadata) “which will allow the understanding of the Content Information over an indefinite period of time”

• A set of Information Objects• In part based on categories discussed in

CPA/RLG task force report (1996)




PreservationDescriptionInformation

Reference Information

ProvenanceInformation

ContextInformation

FixityInformation

PDI Preservation Description Information (Figure 4-16)




• Fixity - supporting data integrity checking mechanisms

• Reference - for supporting identification and location over time

• Context - documenting the relationship of the Content Information to its environment

• Provenance - documents the history of the Content Information






OAIS Information Model

• Also defines:– Archival Information Units and Archival

Information Collections• Recognises the complexity some some

objects, addresses granularity– Information Package transformations

• For Ingest and Access



OAIS - other perspectives

• Preservation– Migration, e.g refreshment, replication,

repackaging, transformation– Preservation of look and feel (e.g., emulation,

virtual machines)• Archive interoperability

– Interaction between OAIS archives (e.g., co-operating and federated archives)

• Examples of existing archives



Implementation fundamentals (1)

• OAIS is a reference model (conceptual framework), NOT a blueprint for system design

• It informs the design of system architectures, the development of systems and components

• It provides common definitions of terms … a common language, means of making comparison

• But it does NOT ensure consistency or interoperability between implementations




• ISO 14721:2003– Follows the Recommendation made available

by the CCSDS– However, earlier versions of the model made

available by the CCSDS informed implementations long before its formal issue by ISO




• Main areas of influence:– Related standards (e.g., CCSDS Archive-

Producer Interface)– Standardising terminology– Compliance and certification– Analysis and comparison of archives– Informing system design– Preservation metadata



OAIS compliance (1)

• Many repositories or preservation tools claim OAIS influence or compliance:– e.g., IBM DIAS, DSpace, OCLC Digital Archive,

METS, the list is endless– LOCKSS System has produced a "formal

statement of conformance to ISO 14721:2003" (lockss.stanford.edu/)

• The OAIS model's own view (OAIS 1.4):– Supporting the information model (OAIS 2.2),– Fulfilling the six mandatory responsibilities (OAIS

3.1)



OAIS compliance (2)

• OAIS Mandatory Responsibilities (recap):– Negotiating and accepting information– Obtaining sufficient control of the information to

ensure long-term preservation– Determining the "designated community" – Ensuring that information is independently

understandable– Following documented policies and procedures – Making the preserved information available



Trusted digital repositories (1)

• OCLC/RLG Digital Archive Attributes Working Group– Trusted Digital Repositories report (2002)

• http://www.rlg.org/legacy/longterm/repositories.pdf

– Recommended the development of a process for the certification of digital repositories

• Audit model• Standards model

– Built upon the OAIS model …



Trusted digital repositories (2)

• Identified specific attributes:– Compliance with OAIS– Administrative responsibility– Organisational viability– Financial sustainability– Technological and procedural suitability– System security– Procedural accountability



Digital repository certification (1)

• RLG-NARA Task Force on Digital Repository Certification– RLG and the US National Archives and

Records Administration– To define certification model and process

• Identify those things that need to be certified (attributes, processes, functions, etc.)

• Develop a certification process (organisational implications)

– Draft list of criteria published (2005)– Led to TRAC (CRL & OCLC, 2007)




• Trusted Repositories Audit & Certification (TRAC): Criteria and Checklist (March 2007)– Organisational infrastructure

• e.g., governance, organisational structures, mandates, policy frameworks, funding systems, contracts and licenses

– Digital Object Management (OAIS functions)• e.g., ingest, metadata, preservation strategies

– Technologies, Technical Infrastructure, & Security




• Test audits (by CRL, DCC, etc.) enabled further refinement of the certification model

• TRAC just one of several audit and certification initiatives:– German nestor initiative– DRAMBORA (DCC and Digital Preservation

Europe), based on risk assessment approach• The aim is now to develop an ISO standard, under

the general aegis of CCSDS (public wiki and mailing list)



The analysis of existing services

• A process that was started in the annexes to the model itself

• Looking at existing services and processes, mapping them to OAIS functional and information model

• Main uses:– Identifying significant gaps– Provides a common language for the

comparison of archives



BADC/APS case study (1)

• British Atmospheric Data Centre– A data centre of the Natural Environment

Research Council (NERC)– Evaluating the use of the CCLRC's Atlas Petabyte

Storage (APS) Service for long-term data storage– Mapping OAIS to combined BADC/APS

• BADC responsible for Ingest and Access• APS responsible for Archival Storage• Jointly responsible for Data Management and

Administration



BADC/APS case study (2)

• Application of OAIS revealed:– Feedback on how well the BADC/APS fulfilled

OAIS mandatory responsibilities– Revealed that AIP needed better definition– Weaknesses identified with the Preservation

Planning role, e.g. little explicit monitoring of technology or of the Designated Community

• OAIS helps to identify limitations• For more details, see: Corney, et al. (2004)

http://www.allhands.org.uk/2004/proceedings/papers/156.pdf



BADC/APS case study (3)Preservation Planning

Ingest

Access

BADC Team

BADC Team

Authorising Authority(BADC or external data

manager)

BADC Support Team

External User

Administration

User Database

Metadata Management

Metadata

Archival Storage

Data

Generate metadata

Ingest files

Volume plans

Format descr.

Discovery Search

Data Access via FTP & HTTP

Handle queries

Manage user

accounts

Corrected files re-ingested

Submitted files

BADC team add metadata

Harvest

New and updated files

Data submission authorisation

Authentication and authorisation

Registration details and updates

Query and response

Query and response

Access request and authorisation

Report on user details

Query, update database

User details

Search & results

Data requests & data

Authentication

Preservation PlanningPreservation Planning

IngestIngest

AccessAccess

BADC TeamBADC Team

BADC TeamBADC Team


manager)


manager)

BADC Support TeamBADC Support Team

External User

AdministrationAdministration

User DatabaseUser Database

Metadata Management

Metadata

Metadata Management

MetadataMetadata

Archival Storage

Data

Archival Storage

DataData

Generate metadataGenerate metadata

Ingest files

Ingest files

Volume plans

Volume plans

Format descr.Format descr.

Discovery Search

Discovery Search



Handle queriesHandle queries

Manage user

accounts

Manage user

accounts

Corrected files re-ingested

Submitted files

BADC team add metadata

Harvest

New and updated files

Data submission authorisation

Authentication and authorisation

Registration details and updates

Query and response

Query and response

Access request and authorisation

Report on user details

Query, update database

User details

Search & results

Data requests & data

Authentication



UKDA and TNA case study (1)

• Project funded by the UK Joint Information Systems Committee (JISC)

• Partners:– UK Data Archive– The National Archives

• Aimed to map UKDA and TNA to OAIS functional and information models, a "use case" for compliance

• Beedham, et al., Assessment of UKDA and TNA Compliance with OAIS and METS Standards (2005)




• Conclusions (1):– Noted that there was no existing methodology

for testing OAIS compliance• Recommended the production of guidelines

or manual– The six OAIS Mandatory Responsibilities are

carried out by almost any well-established archive




• Conclusions (2):– The OAIS Designated Community concept

assumes a identifiable and relatively homogenous user community; this was not the case for either UKDA or TNA

– The relationship between AIPs and DIPs needed clarification

– The OAIS Administration function may be difficult for small archives to fulfil adequately




• Conclusions (3):– Model not scalable - report proposes an 'OAIS

Lite'– Information categories (e.g. PDI) are too

general to allow mapping of metadata elements from other schemas (p. 70)

– But ... the use of OAIS terminology was useful to support communication between UKDA and TNA



Informing system design (1)

• OAIS is not a blueprint for system design– "It is assumed that implementers will use this

reference model as a guide while developing a specific implementation to provide identified services and content" (OAIS 1.4)

• But it has been used to inform the design of systems

– This can be difficult because the model does not generally distinguish between management and technical processes




• Examples:– Systems:

• IBM DIAS (used by Koninklijke Bibliotheek in e-Depot, Deutsche national Bibliothek in KOPAL)

• OCLC Digital Archive Service• aDORe (Los Alamos National Laboratory)• Stanford Digital Repository - preservation

not main focus• MathArc (Cornell UL and SUB Göttingen)




• Examples (continued)– Tools:

• Harvard University Library XML-based Submission Information Package for e-journal content

• Repository software: DSpace, FEDORA, …• DCC Representation Information Repository

and Registry




• A basis for domain-specific modelling:– InterPARES project Preservation Task Force's

"Preserve Electronic Records model"• Formally modelled the specific processes and

functions involved with preserving electronic records

• Developed "… a specification of an OAIS for the specific classes of information objects comprising electronic records and archival aggregates of such records"

• http://www.interpares.org/




• Research projects:– OAIS is the “guiding principle” of CASPAR

(specifically the Representation Information concept)

– CASPAR Conceptual model– Representation Information registries and

repositories



Preservation metadata (1)

• Metadata:– Data about data– Structured information about objects that

supports various types of activity: discovery, retrieval, management, etc.

– Can be a problematic concept• Preservation metadata

– The information a repository uses to support the digital preservation process (PREMIS WG)

– OAIS Information Model influenced PREMIS




• A number of different initiatives and standards:– Reflects different professional perspectives

• The archives and records professions focus on traditional archival principles, e.g. the emerging ISO 23081 (Metadata for records) family of standards

• Other domains largely focused on use and reuse, e.g. of research data, multimedia content, digitised text and images

• PREMIS Data Dictionary focused on 'core' preservation requirements




• PREMIS (Preservation Metadata: Implementation Strategies) Data Dictionary– Cross-domain approach, but broad digital

library influences– Based on older initiatives that were more

explicitly based on OAIS Information Model categories

– Identification of 'core' metadata to support preservation

– Based on its own data model




• OAIS Information Model– Divides the information needed to support

preservation into two categories• Representation Information (key concept)• Preservation Description Information

– Is this metadata?– Some OAIS advocates claim that focus on

Representation Information is the only approach that will work for research data

– Much still to be resolved in this area



Summary (1)

• OAIS is a well established standard:– Standardising the terminology used in digital

preservation process– The analysis and comparison of repositories

(and repository processes)– Informing the design of systems (and tools)– Informing the development of certification

criteria– Informing the design and development of

preservation metadata standards



Summary (2)

• However ...– Still some uncertainty about what OAIS

'conformance' means– There remains the question whether the

standard is applicable in all domains• Archivists involved in the initial development

process, but many others feel that it doesn't adequately represent the archival perspective

– OAIS is just a starting point



Further reading• Reference Model for an Open Archival Information System

(OAIS), CCSDS 650.0-B-1 (2002): http://public.ccsds.org/publications/archive/650x0b1.pdf

• DPC Technology Watch Report on the OAIS model by Brian Lavoie (2004):http://www.dpconline.org/docs/lavoie_OAIS.pdf

• Assessment of UKDA and TNA Compliance with OAIS and METS standards by H. Beedham, et al., (2005):http://www.data-archive.ac.uk/news/publications/oaismets.pdf

• Trusted Repositories Audit & Certification (2007): http://www.crl.edu/PDF/trac.pdf

• DRAMBORA Digital Repository Audit Method Based on Risk Assessment (2007): http://www.repositoryaudit.eu/

• nestor Catalogue of Criteria for Trusted Digital Repositories (2006): urn:nbn:de:0008-2006060703



Acknowledgements• UKOLN is funded by the

Museums, Libraries and Archives Council, the Joint Information Systems Committee (JISC) of the UK higher and further education funding councils, as well as by project funding from the JISC, the European Union, and other sources. UKOLN also receives support from the University of Bath, where it is based: http://www.ukoln.ac.uk/

• The Digital Curation Centre is funded by the Joint Information Systems Committee and the UK Research Councils' e-Science Core Programme: http://www.dcc.ac.uk/