Flexible and Extensible Digital Object and Repository Architecture (FEDORA)

1
Flexible and Extensible Digital Object and
Repository Architecture (FEDORA)
ECDL 98 September 21, 1998
Carl Lagoze Cornell University lagoze_at_cs.cornell.e
du
Sandra Payette Cornell University payette_at_cs.corne
ll.edu
http//www2.cs.cornell.edu/payette/fedora/ecdl98.p
pt
2
Acknowledgments

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

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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

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Digital Library Content

• Simple, familiar content types

• Complex, compound, dynamic content types

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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

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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

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Multiple views of a DigitalObject
Book
DataStream (MIME-typed byte stream)
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Content Type

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

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Disseminator

• A generic component for associating
• a set of behaviors with a DigitalObject.

Content Type Disseminator
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FEDORA DigitalObject
Content-Type Wrapper
Primitive Disseminator
Structural Kernel
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Structure with Dublin Core and Book Interfaces
Book Disseminator
DublinCore Disseminator
application/ MARC
DS1
ListContentTypes
application/ postscript
DS2
Book, DublinCore
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Content Type Principles

• Stability
• Extensibility
• Orthogonality to Structure

How do we attain these in the architecture?
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FEDORA Extensibility Model
Interface
Structure
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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

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Content Disseminator is a Generic Component
Disseminator Attributes
DataStreams DS1 ContentTypeID URNDC1
GetDCField GetDCRecord
DC
application/ MARC
DS1
GetMethods(DC)
application/ postscript
DS2
GetDCField, .
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How Achieve Content-Type Extensibility?
CTID URNDC1
DC
application/ MARC
application/ postscript
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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.

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

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Future Research

• Access Management
• Reliability, security, integrity (DLI2)
• Integration of new community-developed content
  types (DLF)

For more information http//www2.cs.cornell.edu/N
CSTRL/CDLRG/FEDORA.html