1. Flexible and Extensible Digital Object and Repository Architecture (FEDORA) Sandra Payette Cornell University payette@cs.cornell.edu http://www.cs.cornell.edu/payette/presentations/fedora-gdz.ppt Dritter Workshop der Digitalisierungszentren, October 5, 1999

2. Cornell Digital Library Research Group Computer Science Department  Bill Arms  Carl Lagoze  Sandy Payette  Naomi Dushay  David Fielding Affiliates  Anne Kenney (Cornell Library)  Geri Gay (Human Computer Interaction)  CNRI

3. CDLRG - Projects Prism (DLI2) Fedora Harmony (IDL) Dienst and NCSTRL Electronic Scholarly Publishing  D-Lib  Citation Linking (IDL)

4. Library of Congress Cornell Digital Library Digital Library Interoperability

5. Principles for Digital Library Architecture Open Architecture  functionality partitioned into set of well-defined services  services accessible via well-defined protocol Modularization  promotes interoperability  scalable to different clientele (library, informal web) Federation  enable aggregations into logical collections Distribution  of content and services  of administration and management

6. Repository Service Component-Ware Digital Libraries Collection Service Index Service Identifiers Name Service Digital Objects UI Gateway Service Query Mediator Service UI

7. FEDORA Digital Object Model  container for aggregating any digital material  disseminations of complex types  global extensibility mechanisms  access management Repository Service  Service layer for “contained” DigitalObjects  Object lifecycle management  Secure environment  open interface

8. FEDORA: Goals Distribution - of digital content and services Interface Stability - for digital objects Interoperability - for digital objects and repositories Extensibility - naturally evolving type system Flexibility - community-driven type development Security - rights management and access control Preservation - longevity of digital objects

9. FEDORA History Kahn/Wilensky Warwick Framework Distributed Active Relationships Cornell FEDORA (Lagoze, Payette) CNRI Repository (Arms, Blanchi, Overly) CNRI/FEDORA - Interoperability Project UVA - Complex disseminators, distribution Project Prism (DLI2)

10. FEDORA DigitalObjects can be... Simple, familiar entities Complex, compound, dynamic objects

11. Dublin Core Book Diary Future FEDORA DigitalObject Model Internal DataStream MIME-typed stream of bytes Reference DataStream Service Request upon external source Dissemination

12. Disseminator Type A set of behaviors that formally describes the functionality of any global or community-specific notion of content. getSection getArticle getChapter getPage getFrame getLength

13. Disseminator A generic component that associates a set of behaviors with a DigitalObject. Primitive Disseminator Extensible Type Disseminator Generic behaviors Extended behaviors

14. FEDORA DigitalObject application/ MARC application/ postscript Primitive Disseminator image/gif

15. application/ MARC DS 1 application/ postscript DS 2 Primitive Disseminator Client communicates with generic requests Book, DublinCore ListDisseminatorTypes Book Disseminator DublinCore Disseminator GetDissemination (Book.GetPage(1)) GetChapter GetTOC GetPage GetChapter(n), GetPage(n),GetTOC() GetMethods(Book)

16. A Disseminator... GetDCField(Title), GetDCRecord GetMethods(DC) application/ MARC DC DS 1 application/ postscript DS 2 … references a Servlet TYPE DESCRIPTION = DublinCore SERVLET = cornell.dli2/DC-from-MARC … to produce non-generic behaviors for the DigitalObject GetDCField GetDCRecord

17. DigitalObject Interface Stability Mechanism Structure Interface Disseminator Type Servlet-2 Servlet-1 Servlet-3 Mechanisms can be updated or replaced as technology changes... … and the interface to the Digital Object remains stable

18. DigitalObject Extensibility: Adding New Types MechanismStructure Interface Book The same underlying data... Book can be operated on in novel ways… Photo Collection to create new disseminations not originally conceived of for the particular digital object. Photo Collect

19. Extensibility: a look under the hood application/ MARC DC servlet application/ postscript DublinCore Record GetDissemination( GetDCRecord) DC Servlet = URN DC1 DC signature GetDCField GetDCRecord DC MethodList Signature Disseminator URN DC DublinCore Disseminator Type Signature (Interface Definition) DublinCore Mechanism (Servlet) DC Mechanism URN DC1 Servlet Disseminator

20. Proliferation of Disseminator Types We use FEDORA DigitalObjects to store Disseminator Signatures and Servlets. Type Registration (via name service)  a Disseminator Type’s global identifier is … the URN of a DigitalObject containing a Signature  a Servlet’s global identifier is … the URN of a DigitalObject containing a Servlet Types can be globally recognizable and mechanisms can be shared.

21. Repository Interoperable Digital Objects and Repositories Identifiers Name Service RAP Client Image Database System Repository Cornell Library CollectionsAudio/Visual Archive

22. Persistent Identifiers In FEDORA, use them for:  Repositories  DigitalObjects  Disseminator Types  Servlet Mechanisms Benefits:  Ensure uniqueness  Provide stability (location independence)  Promote global extensibility  Promote interoperability Identifiers Name Service

23. Identifiers - A Brief Primer IETF Uniform Resource Name (URN) Spec Naming Scheme  The policies and procedures for creating and assigning URNs within a particular domain. Resolution System  A system that translates URNs into their location- specific identifiers (e.g., URLs). Registries  A set of global directories that provide information on which resolution systems can translate any particular URN.

24. Identifiers - Existing Solutions CNRI’s Handle System  good implementation of URN specification  1 Handle >> one or more locations  resolve to different data types (URL, IOR,…) OCLC’s PURL  persistent URLs, not really URNs  1 PURL >> only one location (a HTTP redirect) Community-specific Initiatives  Digital Object Identifier (DOI) - publishers Handle System + Rights Metadata  PubMedID - Medline  BibCode - astro-physics journals

25. FEDORA Status Reference Implementation  CORBA IDL defines open interfaces for Repository Access Protocol (RAP)  Java/CORBA repository and clients Collaborations  CNRI core design and interoperability complex disseminations (dynamic)  U of Virginia web integration complex disseminations (e.g., e-texts)

26. New Research DLI2 - Project Prism  security (associating enforceable policies and mechanisms with DigitalObjects)  preservation (enable long-term survival of DigitalObjects in distributed environment) IDL - Harmony  aggregation and interaction of multiple, complex metadata sets in DigitalObjects  RDF and XML

27. PRISM Security Policy Enforcement Challenges  what is enforceable?  distributed object environment  interoperability and extensibility Monitor all operations, generic and extended Enforce a wide array of policies  basic security violations  rights management  access control application/ MARC text/x-acl DC GetDCField GetDCRecord

28. PRISM: Preservation Handles Preservation Service Fedora Repositories

29. PRISM: Preservation Policy Enforcement preservation metadata Preserve P DS 1 application/ postscript DS 2 Book Preservation Service Monitors DigitalObject state and catches unacceptable, or risky transitions Preservation Surrogate Object

30. References Payette, Blanchi, Lagoze, and Overly: Interoperability for Digital Objects and Repositories: The Cornell/CNRI Experiments, D-Lib Magazine, May 1999. http://www.dlib.org/dlib/may99/payette/05payette.html Payette and Lagoze: Flexible and Extensible Digital Object and Repository Architecture (FEDORA), ECDL 1998. http://www.cs.cornell.edu/payette/papers/ECDL98/FEDORA.html Lagoze and Payette: An Infrastructure for Open-Architecture Digital Libraries http://ncstrl.cs.cornell.edu/Dienst/UI/1.0/Display/ncstrl.cornell/TR98-1690 Daniel, Lagoze, and Payette, A Metadata Architecture for Digital Libraries, IEEE ADL 1998. http://www.cs.cornell.edu/lagoze/papers/ADL98/dar- adl.html FEDORA Home Page http://www.cs.cornell.edu/NCSTRL/CDLRG/FEDORA.html Payette: Persistent Identifiers on the Digital Terrain, RLG DigiNews, April 1998, Volume 2, Number 2. http://www.rlg.org/preserv/diginews/diginews22.html