a distributed architecture for building federated digital libraries

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Harokopio University of Athens – Department of Informatics and Harokopio University of Athens – Department of Informatics and Telematics Telematics HAROKOPIO HAROKOPIO UNIVERSITY UNIVERSITY A Distributed Architecture for A Distributed Architecture for Building Building Federated Digital Libraries Federated Digital Libraries Mara Nikolaidou Department of Informatics and Telematics, Harokopio University of Athens George Pyrounakis Department of Informatics and Telecommunications, University of Athens euroCRIS Meeting, Athens 11-13 May 2009 euroCRIS Meeting, Athens 11-13 May 2009

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HAROKOPIO UNIVERSITY. A Distributed Architecture for Building Federated Digital Libraries. Mara Nikolaidou Department of Informatics and Telematics, Harokopio University of Athens George Pyrounakis Department of Informatics and Telecommunications, University of Athens. - PowerPoint PPT Presentation

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Page 1: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

HAROKOPIOHAROKOPIOUNIVERSITY UNIVERSITY

A Distributed Architecture for Building A Distributed Architecture for Building Federated Digital LibrariesFederated Digital Libraries

Mara NikolaidouDepartment of Informatics and Telematics,

Harokopio University of Athens

George Pyrounakis Department of Informatics and Telecommunications,

University of Athens

euroCRIS Meeting, Athens 11-13 May 2009euroCRIS Meeting, Athens 11-13 May 2009

Page 2: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

Current State in Federated Digital LibrariesCurrent State in Federated Digital Libraries

A central server harvests metadata from the federation repositories

In most cases Open Archive Initiative Protocol for Metadata Harvesting (OAI-PMH) is used

Digital library services are usually dependent on the repository software

Difficulty to build advanced services in a federated environment

Functionality offered by federated digital libraries is not rich

Page 3: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

DL services

DR

OAI-PMHProvider

DR DR

DR

OAI-PMHHarvester

OAI-PMHProvider

OAI-PMHProvider

Architecture Using OAI-PMHArchitecture Using OAI-PMH

Page 4: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

DL Services not supportedDL Services not supported

Workflows for submitting, editing and publishing digital objects

Management of user access policies applied on digital objects and their components

Management of digital collections Digital content handling (conversion, watermarks,

compression etc.) Preservation policies for digital content

Page 5: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

Middleware and Distributed ArchitecturesMiddleware and Distributed Architectures

Current architectural structures (Web Services, CORBA, etc) introduce the concept middleware in order to abstract digital objects. The abstraction separates the physical (stored) from the logical representation of objects

We adopt a similar approach to create a middleware that interprets the structure and semantics of digital objects stored in different repository software located in multiple servers

Using Harvesting digital objects are imported to a central server in a simplified form and the DL services are built on top of that.

A DL middleware preserves the role of the “interpreter” between the DL services and the digital objects that remain located in there local repositories.

Page 6: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

DL services

DR

connector

DR DR

middleware

DL services

connector connector

middleware API

DL Architecture Using a MiddlewareDL Architecture Using a Middleware

Page 7: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

Proposed ConceptsProposed Concepts

A middleware is proposed for the creation of federated DLs called Digital Object Abstraction Layer (DOAL)Digital Object Abstraction Layer (DOAL)

ScopeScope Build federated digital libraries Create reusable digital library services

DOAL provides an API to DL services, which use an abstract but semantically-rich form of digital objects, independent from the repository that are stored in.

DOAL should work over heterogeneous repository software. Digital Object notion within DOAL should be handled

independently from its stored form (or forms).

Page 8: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

Abstract Digital ObjectsAbstract Digital Objects

DOAL uses an abstract form of digital objects that retain their semantics (metadata sets, digital content, relations, behavior) and

Hides their repository-dependent characteristics including the location of the stored digital object, the repository software used for its storage and the encoding used for its serialization.

Abstraction of digital objects is realized using the Digital Object Prototype (DOP) Mechanism

Page 9: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

DOAL BenefitsDOAL Benefits

Abstracts the serialized digital object in a form manageable by DL services independently of the repository software where is stored

Associates digital objects to their DOP, so they are handled in a common manner by the DL services according to the their type

Homogenizes the digital collections of different repositories that are part of a federated DL

Distributed Digital Objects (DDOs) are used which parts are stored in multiple heterogeneous repositories

Page 10: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

Pergamos Digital LibraryPergamos Digital Library

The concept of DOP has been implemented in Pergamos Digital Library by the Libraries Computer Center of the University of Athens

The DL is able to host heterogeneous digital collections using different metadata, digital content, hierarchies and views

A common web interface for all collections is used by cataloguers as long as end users

A type is assigned to each digital object using the notion of DOP

Page 11: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

Pergamos Architecture (I)Pergamos Architecture (I)

Centralized 3-tier Architecture Fedora Digital Repository version 2.0 is used as a

core for the storage and retrieval of digital objects DOP Mechanism is responsible for the abstraction of

digital objects based on the assigned type The Application Logic Layer uses the abstract digital

objects, which are semantically rich

Page 12: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

Pergamos Architecture (II)Pergamos Architecture (II)

Page 13: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

Pergamos CollectionsPergamos Collections

Pergamos is hosting four digital collections in http://pergamos.lib.uoa.gr Historical Archive of the University of Athens Folklore Collection Theatrical Collection Psachos Music Library Collection

Eight more collections are ready to be published (papyri, medical images, mineralogy, published elections, etc.)

Page 14: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

Pergamos Screenshot (I)Pergamos Screenshot (I)

Page 15: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

Pergamos Screenshot (I)Pergamos Screenshot (I)

Page 16: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

DDO Simple ExampleDDO Simple Example

DDO 1

DC

THUMB

Node A Node B

SDO xWEB

HQ

SDO y

DOAL

DR DR

Page 17: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

WorkflowManager

FedoraRepository

DSpaceRepository

CustomRepository

Browsing -Searching

DOAL API

DDODDO

AbstractionMechanismAbstractionMechanism

DDODDODDODDO

Personalization

DDO Pool

DDO RegistryDDO Registry

ConnectorsPool

ConnectorsPool

Object Editor

DR RegistryDR Registry

DOP RegistryDOP Registry

DL

Ser

vice

sD

OA

LR

ep

osito

ries

DOAL ArchitectureDOAL Architecture

Page 18: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

DOAL ModulesDOAL Modules

Registries keep information about DDOs, Digital Repositories and DOPs

Connectors are implemented for each repository software participating in the federated digital library

Abstraction Mechanism is responsible for the abstraction of digital objects according to their type (described in DOP)

DDO Pool holds the DDO instances which are available to be used by the DL services

Page 19: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

Distributed Digital Object InstantiationDistributed Digital Object Instantiation

Page 20: A Distributed Architecture for Building  Federated Digital Libraries

Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics

Current StateCurrent State

Implementing connectors for Fedora and DSpace

Implementing DOAL RegistryDL RegistryDDO – DOP Registry

Implementing DDO Handlers

First version of DOAL expected by February 2010