1. Flexible and Extensible Digital Object and Repository Architecture (FEDORA)
ECDL ‘98
September 21, 1998
Carl Lagoze
Cornell University
Sandra Payette
Cornell University

2. Acknowledgments Warwick Framework - Daniel, Lynch
Distributed Active Relationships - Daniel
CNRI Digital Object Architecture - Kahn/Wilensky, Arms/Blanchi/Overly
DARPA funded project

3. Introduction
Part of our broader effort to develop a component-ware digital library architecture
core service to provide a reliable and secure means to store and disseminate digital content
interoperability with other core services, including indexing, naming, collection
FEDORA addresses the complex, contextual, and evolutionary nature of digital library content

4. Digital Library Content
Simple, familiar content types
Complex, compound, dynamic content types

5. What are the interesting problems here?
Normalization of digital library content - order the chaos
Flexible notions of content while ensuring interoperability
Stable interfaces as underlying mechanisms change
Naturally evolving content type system - extensibility
Community-driven content type development
Complex aggregations of distributed content
Rights management - leverage existing/future schemes

6. FEDORA DigitalObject: container for content
Structure (raw data structure)
Interface (content views)
Mechanisms (executables)
Repository: logical service
Service layer for “contained” DigitalObjects
Object lifecycle management
Secure environment for running mobile code

7. Multiple “views” of a DigitalObject
Book
Future
Diary
Dublin
Core
DataStream (MIME-typed byte stream)

8. Content Type
A set of behaviors that formally describes the functionality of any global or domain-specific notion of content.

9. Disseminator A generic component for associating
a set of behaviors with a DigitalObject.
Primitive
Disseminator
Content Type
Disseminator

10. FEDORA DigitalObject Content-Type Wrapper Structural Kernel Primitive
application/
postscript
MARC
Primitive
Disseminator
Structural Kernel

11. Structure with Dublin Core and Book Interfaces
Disseminator
DublinCore
Disseminator
application/
MARC
DS1
ListContentTypes
application/
postscript
DS2
Book, DublinCore

12. Content Type Principles
Stability
Extensibility
Orthogonality to Structure
How do we attain these in the architecture?

13. FEDORA Extensibility Model
Mechanism
Content Type
Structure
Interface

14. Content Type Extensibility
FEDORA uses its own architectural abstractions to support content-type extensibility
Content types become persistent, named entities in the digital library infrastructure

15. Content Disseminator is a Generic Component
Disseminator Attributes:
DataStreams = DS1
ContentTypeID = URNDC1
GetDCField
GetDCRecord DC
application/
MARC
DS1
GetMethods(DC)
application/
postscript
DS2
GetDCField, ….

16. How Achieve Content-Type Extensibility?
DC servlet DC
Mechanism
Servlet
Disseminator
URNDC1
CTID = URNDC1 DC
application/
MARC
GetDissemination(
GetDCRecord)
application/
postscript
DublinCore
Record DC
MethodList
Signature
Disseminator
URNDC
DC signature
GetDCField
GetDCRecord

17. Registration and Proliferation of Content Types
A content type becomes registered when the URN of the DigitalObject that disseminates its signature is registered (in a DL name service)
A content type becomes usable when the URN of the DigitalObject that disseminates its servlet is registered
Other DigitalObjects can utilize content types by referencing them by these URNs.

18. Access Management Must have facilities to protect content
No single solution
Association of existing, external rights management schemes
Accommodate new schemes
FEDORA applies same extensibility model
to rights management ...

19. AccessManager Mechanisms
Disseminator protected by AccessManager
URN1
URNACL1
GetDCField
GetDCRecord DC
application/
MARC
ACL
Mechanism
text/x-acl
Servlet
Disseminator
External Servlet Utilized

20. Current Status Full reference implementation
CORBA IDL defines all component interfaces
Java/CORBA prototype system complete
Developed common IDL with CNRI
Merger of RAP and FEDORA IDL
Interoperability Experiments (Fall 1998)

21. Future Research Access Management
Reliability, security, integrity (DLI2)
Integration of new community-developed content types (DLF)
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