1. Flexible and Extensible Digital Object and Repository Architecture (FEDORA) Sandra Payette Cornell University payette@cs.cornell.edu CS 502 Computing Methods for Digital Libraries April 20, 2000

2. Repository Services Component-Ware Digital Libraries Collection Services Index Services Handles Name Service Digital Objects User Gateway Service

3. 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

4. FEDORA Digital Object  container for aggregating any digital material  disseminations of complex types  global extensibility mechanisms Repository  Service layer for “contained” DigitalObjects  Object lifecycle management  Secure environment for running mobile code

5. FEDORA History Digital Object vision (Kahn/Wilensky) Warwick Framework (container model) Distributed Active Relationships (Lagoze) Cornell FEDORA (Payette, Lagoze) CNRI Repository (Arms, Blanchi, Overly) CNRI/FEDORA Interoperability Project UVA/FEDORA (Staples, Weyland) - Complex disseminators, XML/XSL, web integration Project Prism (DLI2) – Security, preservation Lecture Browser (Mukhopadhyay, Newman)

6. Fedora DigitalObjects can be... Simple, familiar entities Complex, compound, dynamic objects

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

8. Digital Object is... recognizable by what it can do getChapter getPage getTrack getLabel getSection getArticle getFrame getLength

9. Disseminator Type A set of behaviors that formally describes the functionality of any global or community-specific notion of content.

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

11. FEDORA DigitalObject application/ postscript application/ MARC Primitive Disseminator Structural Kernel Extensible Behavior Layer

12. 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)

13. DigitalObject Interface Stability Mechanism Structure Interface Disseminator Type Mechanisms can be updated or replaced as technology changes... … and the interface to the Digital Object remains stable

14. 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

15. A Disseminator is a Generic Component... … that references another FEDORA DigitalObject that disseminates a servlet GetDCField(e), GetDCRecord GetMethods(DC) application/ MARC GetDCField GetDCRecord DC DS 1 application/ postscript DS 2 DataStreams = DS 1 TypeID = URN DC1 … to produce non-generic behaviors

16. Extensibility: a look under the hood application/ MARC DC servlet application/ postscript DublinCore Record GetDissemination( GetDCRecord) DC CTID = URN DC1 DC signature GetDCField GetDCRecord DC MethodList Signature Disseminator URN DC DC Mechanism Servlet Disseminator URN DC1 Digital Object attains its extended behaviors through association and delegation

17. Registration and Proliferation of Disseminator Types Disseminator Types registered in the Handle System  visible when URN of a Signature is registered  usable when URN of a Servlet is registered Other DigitalObjects can use Disseminator Types by referencing these URNs. Handle System Fedora Repository

18. Big Picture: Cooperation among non-cooperating sources Lesson 1 module GetDissemination( GetLesson(1)) Learning Object Library Catalog Museum Image Database Video Archive

19. Repository Big Picture: Interoperable Repositories Handles Name Service Cornell CS Lectures RAP Client NCSTRL Repository Cornell Library Collections

20. Current Status FEDORA Implementation  CORBA IDL defines all component interfaces  Java/CORBA reference implementation (Fedora server and GUI client). Experimental Disseminator Types  Dublin Core  Image  Article/Technical Report  Book (with CNRI / Library of Congress)  Lecture Object (video, slides)

21. Current Work: Security Access Control for Digital Objects Monitor all operations, generic and extended Security Automata (Schneider) Policy-carrying, policy-enforcing Digital Objects using :  PoET (Erlingsson and Schneider)  Fedora (Payette, Lagoze, Dushay)

22. AccessManager MARC policy DC Servlet Disseminator URN DC1 URN 1 GetDCField GetDCRecord Disseminator protected by an AccessManager. The DC Servlet is a piece of mobile code that is dynamically “in-lined” with the policy for the object. Remote Servlet Utilized DC Mechanism

23. Future Work: Preservation Augmented DigitalObjects preservation metadata Preserve P DS 1 application/ postscript DS 2 Book Preservation Service Sets of methods we will define

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

25. References FEDORA Home Page, http://www.cs.cornell.edu/cdlrg/fedora.html 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, Technical Report, 1998 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

26. References cont. Schneider, Fred B., Enforceable Security Policies, Technical Report, Department of Computer Science, Cornell University, July 1999, http://cs-tr.cs.cornell.edu:80/Dienst/UI/1.0/Display/ncstrl.cornell/TR99-1759 Erlingsson, Ulfar and Fred Schneider, SASI Enforcement of Security Policies: A Retrospective, Technical Report, Department of Computer Science, Cornell University, July 1999, http://cs-tr.cs.cornell.edu:80/Dienst/UI/1.0/Display/ncstrl.cornell/TR99-1758 Erlingsson, Ulfar and Fred Schneider, IRM Enforcement of Java Stack Inspection, Technical Report, Department of Computer Science, Cornell University, February 2000, http://cs-tr.cs.cornell.edu:80/Dienst/UI/1.0/Display/ncstrl.cornell/TR2000-1786