Flexible and Extensible Digital Object and Repository Architecture (FEDORA)

1
Flexible and Extensible Digital Object and
Repository Architecture (FEDORA)
Sandra Payette Cornell University payette_at_cs.corne
ll.edu
Dritter Workshop der Digitalisierungszentren,
October 5, 1999
http//www.cs.cornell.edu/payette/presentations/fe
dora-gdz.ppt
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
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
Component-Ware Digital Libraries
UI Gateway Service
Name Service
Identifiers
Collection Service
Query Mediator Service
Index Service
Repository Service
Digital Objects
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
FEDORA DigitalObject Model
MIME-typed stream of bytes
Book
Dissemination
Service Request upon external source
Internal DataStream
Reference DataStream
12
Disseminator Type

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

getSection getArticle
13
Disseminator

• A generic component that associates
• a set of behaviors with a DigitalObject.

Extensible Type Disseminator
Generic behaviors
Extended behaviors
14
FEDORA DigitalObject
application/ MARC
application/ postscript
image/gif
image/gif
image/gif
image/gif
Primitive Disseminator
15
Client communicates with generic requests
GetChapter GetTOC GetPage
application/ MARC
DS1
Primitive Disseminator
application/ postscript
DS2
16
A Disseminator...
GetDCField GetDCRecord
DC
application/ MARC
DS1
GetMethods(DC)
application/ postscript
DS2
GetDCField(Title), GetDCRecord
17
DigitalObject Interface Stability
Disseminator Type
Interface
Mechanism
18
DigitalObject Extensibility Adding New Types
Book
The same underlying data...
Mechanism
Structure
Interface
19
Extensibility a look under the hood
Servlet URNDC1
DC
application/ MARC
application/ postscript
20
Proliferation of Disseminator Types

• We use FEDORA DigitalObjects to store
  Disseminator Signatures and Servlets.
• Type Registration (via name service)
• a Disseminator Types global identifier is
• the URN of a DigitalObject containing a
  Signature
• a Servlets global identifier is
• the URN of a DigitalObject containing a Servlet

Types can be globally recognizable and mechanisms
can be shared.
21
Interoperable Digital Objects and Repositories
RAP Client
Name Service
Repository
Identifiers
Cornell Library Collections
Audio/Visual Archive
Image Database System
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

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

• CNRIs Handle System
• good implementation of URN specification
• 1 Handle gtgt one or more locations
• resolve to different data types (URL, IOR,)
• OCLCs PURL
• persistent URLs, not really URNs
• 1 PURL gtgt 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

GetDCField GetDCRecord
DC
application/ MARC
text/x-acl
28
PRISM Preservation
Fedora Repositories
Preservation Service
29
PRISM Preservation Policy Enforcement
Preservation Surrogate Object
Monitors DigitalObject state and catches
unacceptable, or risky transitions
Preserve
Book
P
DS1
preservation metadata
Preservation Service
application/ postscript
DS2
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/pay
  ette/papers/ECDL98/FEDORA.html
• Lagoze and Payette An Infrastructure for
  Open-Architecture Digital Libraries
  http//ncstrl.cs.cornell.edu/Dienst/UI/1.0/Displa
  y/ncstrl.cornell/TR98-1690
• Daniel, Lagoze, and Payette, A Metadata
  Architecture for Digital Libraries, IEEE ADL
  1998. http//www.cs.cornell.edu/lagoze/papers/ADL9
  8/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/digi
  news22.html