1. The Fedora Project March 19, 2003 ISTEC Symposium, Brazil
Sandy Payette
Cornell Information Science

2. The Problem of Complex Content
Motivation
The Problem of Complex Content

3. Digital Library Content not just documents ...
Some familiar objects
Complex, compound, dynamic objects

4. Research Questions
How can clients interact with heterogeneous collections of complex objects in a simple and interoperable manner?
How can complex objects be designed to be both generic and genre-specific at the same time?
How can we associate services and tools with objects to provide different presentations or transformations of the object content?
How can we associate fine-grained access control policies with specific objects, or with groups of objects?
How can we facilitate the long-term management and preservation of complex objects that have dependencies on distributed content and services?

5. The Flexible Extensible Digital Object Repository Architecture (FEDORA)
DARPA and NSF-funded research at Cornell (1997-present)
CORBA-based reference implementation (Payette/Lagoze)
Extensive interoperability testing (with Arms/Blanchi/Overly)
Policy Enforcement (Payette/Schneider)
Interpreted and re-implemented at U of Virginia (1999-)
Simple web-oriented implementation, focused on access to collections
Java servlet and relational db
Testbed of 10,000,000 objects with performance metrics ( )
Mellon-Funded FEDORA Software(2002-)
University of Virginia and Cornell - joint development
Open source
Web services and XML
Mediation of distributed services
Preservation focus

6. Fedora: Key Features
Open System – public APIs, exposed as web services
Flexible Digital Object Model
XML submission and storage (METS Schema)
Local and distributed content
Data (any type) and metadata (any schema – DC, other)
Supports inter-relationships among objects
Behavior “contracts” for objects
Associate services with objects
Objects can provide launch-pad or tool to use object content
Repository System:
Management Service - manage digital resources, metadata, as well as computer programs, services and tools that support them
Access Service – repository search and object disseminations
Mediation - interacts with other distributed web services for content transformation and presentation
OAI Provider
Access Control
Preservation service (future release)

7. Requirements: Heterogeneous Digital Collections
Books
Rare Books
Multimedia
Music
E-texts
Maps
Photographs
Statistics
Video
Art
Manuscripts
Data
Images
3-D Objects
Journals
Sound Effects

8. Shortcomings of commercial digital library products
Narrow focus on specific media formats (e.g. image databases, document management)
Fail to effectively address interrelationships among digital entities
Fail to address interoperability; no open interfaces to facilitate sharing of services; no standard protocols for cross-system interoperability
Fail to provide facilities for managing programs and tools that are integral to delivering digital content.
Not extensible; does not enable easy integration of new tools and services
Do not address fine-grained access control and preservation issues.

9. The Fedora Architecture
Digital Object Model
The Repository
Web Services

10. FEDORA Basic Object Architecture
Digital Object Model
Container to aggregate digital content of any type
Data or metadata
Local or distributed
Behavior “contracts”
Definitions of abstract operations
Fulfillment via bindings to external services
Enables multiple “disseminations” of content

11. Digital Object Model Functional View
Dynamic
data
Application
services

12. Globally unique persistent id
Digital Object Model Architectural View
Globally unique persistent id
Persistent ID (
PID )
Public view: access methods for obtaining “disseminations” of digital object content
Disseminators
Internal view: metadata necessary to manage the object
System
Metadata
Datastreams
Protected view: content that makes up the “basis” of the object

13. Digital Object Model Example Disseminators
Get Profile
List Items
Get Item
List Methods
Get DC Record
Persistent ID (
PID )
Disseminators
Default
Simple Image
System
Metadata
Get Thumbnail
Get Medium
Get High
Get VeryHigh
Datastreams

14. Behavior Definition Object Behavior Mechanism Object
Object Behavior Contracts
Behavior Definition Object
Persistent ID (PID)
Behavior Definition
Metadata
System
Datastreams
behavior
subscription
Data Object
Persistent ID (PID)
Disseminators
Datastreams
System Metadata
behavior contract
data contract
Persistent ID (PID)
Service Binding
Metadata (WSDL)
System
Metadata
Datastreams
Web
Service
Behavior Mechanism Object

15. FEDORA Basic Repository Architecture
Repository System
Object Management
Lifecycle (Ingest/create  Store  Delete  Approve  Purge)
Validation
PID Generation
Version management
Access Control
Preservation support
Object Access
Object Dissemination
Object Reflection
Service Mediation

16. Fedora Implementation
Understanding the system implementation
Web Services
Server Design

17. What is a Web Service?
A distributed application that runs over the internet.
A web application that publishes an open interface through which clients can send requests and received responses
Standards
Transport protocol: HTTP, others
Messaging protocol: SOAP, HTTP GET/POST
Message encoding: XML
Service description: WSDL

18. Fedora and Web Services
Fedora Repository system is a web service
Access/Search (API-A) and Management (API-M)
Service descriptions published using WSDL
Both SOAP and HTTP bindings
Back-end services
Digital object behaviors implemented as linkages to other distributed web services
Service binding metadata (WSDL) stored in special Fedora Behavior Mechanism objects.
Fedora acts as mediator to these services.

19. Fedora Repository System Client and Web Service Interactions
Frontend
Backend
Fedora
Repository
System
Content
Transform
Service
user
application
client
application
client
Service
Web Service
Web Service Dispatch
Content
Transform
Service
user
browser
web
Service

20. 3-Tiered Architecture Modular & Extensible System Diagram
Fedora Server Design
3-Tiered Architecture
Modular & Extensible
System Diagram

21. Server Design: 3 Layers Interface Service Exposure
API-A, API-M, pure HTTP and SOAP via HTTP.
Application Logic
Implements requests in terms of the Fedora object model.
Storage
Database, File system, Object serializations and cache(s).

22. Fedora System Diagram

23. Open Source Fedora: Implementation Technologies
Fedora Web Services Layer
Apache Axis for SOAP over HTTP
Apache Tomcat 4.1
Core Repository System
Sun Java J2SDK1.4
Xerces for XML parsing and validation
Saxon 6.5 for XSLT transformation
Schematron 1.5 for validation
MySQL and Mckoi relational database
Deployment Platforms
Windows 2000, NT, XP
Solaris
Linux

24. DEMO: Use Cases
Connect to Repository

25. Release Plan Phase 1 – Fedora 1.0 (May 1, 2003 public)
Advanced Access Control
Preservation Service
R2R Repository Federation
Reliability
Fault tolerance
Mirroring and replication
Performance tuning
Caching
Load balancing
Storage scalability

26. Deployment Partners Los Alamos National Laboratory: Research Library
Library of Congress: Motion Picture and Recorded Sound Division
Indiana University: Digital Library group
Kings College London: Humanities Computing
NYU: Humanities Computing
Northwestern University: Academic Computing
Oxford: Oxford Digital Library and The Refugee Studies Center
Tufts: Digital Collections and Archives Department

27. More Information