a distributed architecture for building federated digital libraries
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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 PresentationTRANSCRIPT
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
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
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
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
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.
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
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).
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
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
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
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
Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics
Pergamos Architecture (II)Pergamos Architecture (II)
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.)
Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics
Pergamos Screenshot (I)Pergamos Screenshot (I)
Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics
Pergamos Screenshot (I)Pergamos Screenshot (I)
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
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
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
Harokopio University of Athens – Department of Informatics and TelematicsHarokopio University of Athens – Department of Informatics and Telematics
Distributed Digital Object InstantiationDistributed Digital Object Instantiation
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