Fourteenth International Conference on Grey Literature - Rome, 2012
Alessia Bardi, Sandro La Bruzzo, Paolo Manghiname.surname@isti.cnr.it
http://nemis.isti.cnr.it/groups/infrascience
CUSTOMIZEDOAI-ORE AND OAI-PMHEXPORTSOF COMPOUND OBJECTS FORFEDORA REPOSITORIES
SCENARIO AND MOTIVATIONS
•Digital Library Systems (DLSs) need to export content
•Export of compound objects: packages of informationobjects with an identity
•OAI protocols (typical solution)
•DL management systems (DLMSs) need to support exportprotocols
•DLMS issues:
•Absence of OAI-exports: some DLMS do not providesupport for OAI protocols (Relational Databases)
•Pre-defined OAI exports of compound objects: shapeof objects as exported by OAI protocols is pre-definedby the DLMS (Fedora)
Fourteenth International Conference on Grey Literature - Rome, 2012
OBJECT EXCHANGE PROTOCOLS
OAI-PMH
OAI-ORE
Exchange subject
Metadata
Resource
Graph-based datamodel
No
Yes
Data Model
SetItemMetadataPrefix
AggregationAggregatedResourceProxy
Protocol
6 OAI Verbs onHTTP
HTTP
Data Serialization
XML
RDF (XML, ATOM)
Deleted recordsmanagement
Yes
No
Fourteenth International Conference on Grey Literature - Rome, 2012
FEDORA: FLEXIBLE EXTENSIBLE DIGITALOBJECT REPOSITORY ARCHITECTURE
A Fedora instance manages graphs of Data Objects
Data Objects conform to Content Models
Content Models define:
•Type and name of mandatory datastreams (files)
•Allowed relationships to other Data Objects
Fourteenth International Conference on Grey Literature - Rome, 2012
Graphs ofContent Models
Graphs ofData Objects
Compliant to
Digital Librarydocumentmodelimplementation
FEDORA
FEDORA OBJECTS AND COMPOUNDOBJECTS
Fourteenth International Conference on Grey Literature - Rome, 2012
CM_article
ds: ART, PDFds: DC, XML
CM_data
ds: DATA, binaryds: DC, XML
ds: DDI, XML
USED_BY
GENERATED_BY
GENERATES
USES
hasModel
Documentmodel:implementationwith FedoraContent Models
Fedorainstance:graphs of
Fedora DataObjects
Art2
ds:DC
ds:ART
Data1
ds:DC
ds:DATA
USED_BY
Art1
ds:ART
ds:DC
GENERATES
GENERATED_BY
USES
ds:DDI
hasModel
hasModel
Compound
Object 1
Compound
Object 2
FEDORA OBJECTS AND COMPOUNDOBJECTS
Fourteenth International Conference on Grey Literature - Rome, 2012
CM_article
ds: ART, PDFds: DC, XML
CM_data
ds: DATA, binaryds: DC, XML
ds: DDI, XML
USED_BY
GENERATED_BY
GENERATES
USES
Documentmodel:implementationwith FedoraContent Models
hasModel
Fedorainstance:graphs of
Fedora DataObjects
Art2
ds:DC
ds:ART
Data1
ds:DC
ds:DATA
USED_BY
Art1
ds:ART
ds:DC
GENERATES
GENERATED_BY
USES
ds:DDI
hasModel
hasModel
Compound
Object 1
Compound
Object 2
Basic OAI-PMH Provider
OAI Provider
PMH-Set
Each Fedora Data Object is annotated withrelationships to the Sets it belongs to
PMH-Item
Fedora DataObject
Fedora Data Object
PMH MetadataRecords
Datastream
Datastream
PMH Metadata Format
Dublin Core
Any format in existingdatastreams
Compound ObjectBoundaries
Fedora DataObject
Fedora Data Object
EXISTING OAI-PMH SOLUTIONS
Fourteenth International Conference on Grey Literature - Rome, 2012
EXISTING OAI-ORE SOLUTIONS
Fourteenth International Conference on Grey Literature - Rome, 2012
OREProvider
Fedora2ORE
ORE Aggregation
Defined by annotation
Sub graph visited startingfrom a given Fedora DataObject
ORE AggregatedResources
Datastreams with agiven name (e.g., DC)
Fedora Data Objects in thesub graph
ORE Proxy
not supported
Relationships betweenAggregated Resources
NO
Compound ObjectBoundaries
Fedora Data Objectsannotated with thesame tag
Navigation depth
EXISTING OAI-PMH SOLUTIONS
•OAI-PMH Set: defined by annotations in each Fedora Data Object
•OAI-PMH Item granularity: Fedora Data Object
•OAI-PMH Metadata records: XML Datastreams
Fourteenth International Conference on Grey Literature -Rome, 2012
USES
Art2
ds:DC
ds:ART
Data1
ds:DC
ds:DATA
USED_BY
Art1
ds:ART
ds:DC
GENERATES
GENERATED_BY
ds:DDI
OAI-PMH Set
ItemArt1
•DC
ItemArt2
•DC
Item Data1
•DC
•DDI
EXISTING OAI-ORE SOLUTIONS:OREPROVIDER
Fourteenth International Conference on Grey Literature - Rome, 2012
USES
Art2
ds:DC
ds:ART
Data1
ds:DC
ds:DATA
USED_BY
Art1
ds:ART
ds:DC
GENERATES
GENERATED_BY
ds:DDI
http://<fedoraServer>/objects/Art1/datastreams/DC/content
Aggr
http://<fedoraServer>/objects/Art2/datastreams/DC/content
http://<fedoraServer>/objects/Data1/datastreams/DC/content
Start FDO: Art1, navigation depth: 2
EXISTING OAI-ORE SOLUTIONS:FEDORA2ORE
•OAI-ORE Aggregation: graph visited from a given start Fedora DataObject
•OAI-ORE Aggregated resources: XML representation of visitedFedora Data Objects
•OAI-ORE Proxy: not supported no semantic relationships
Fourteenth International Conference on Grey Literature - Rome, 2012
USES
Art2
ds:DC
ds:ART
Data1
ds:DC
ds:DATA
USED_BY
Art1
ds:ART
ds:DC
GENERATES
GENERATED_BY
ds:DDI
http://<fedoraServer>/objects/Data1
Aggr
http://<fedoraServer>/objects/Art1
Start FDO: Art1, navigation depth: 1
exporting compound objects in fedora– solutions and limits
•Current solutions for OAI-PMH exports on Fedora...
•...export OAI-items with the granularity of a Fedora Data Object
•...support the export of XML contained in datastreams
•Current solutions for OAI-ORE exports on Fedora…
•…exclude relationships and their semantics
•... allow limited customization of the structure of the compoundobjects (e.g., navigation depth)
•…pre-define the structure of the exported objects
•OAIzer works on any Fedora instance with Content Models:
•ORE exports include relationships and their semantics
•Structure of exported objects is fully customizable
•OAI-PMH metadata formats can be generated on request(requires the configuration of an appropriate transformation rule)
Fourteenth International Conference on Grey Literature - Rome, 2012
EXPORTING COMPOUND OBJECTS:THE OAIZER SOLUTION
•OAIzer is a generic software for the customization ofcompound objects in Digital Libraries
•Software layer over the Digital Library Management System
•ORE exports include relationships and their semantics
•PMH metadata formats can be generated on request
•DB-OAIzer:
•works on RDBMS;
•prototype in the OpenAIRE project, to be integrated withOpenAIRE+ (Open Access Infrastructure for Research in Europe)
•Fedora-OAIzer:
•for Digital Library Systems based on Fedora frameworks withContent Models
Fourteenth International Conference on Grey Literature - Rome, 2012
FEDORA-OAIZER:HIGH-LEVEL ARCHITECTURE
Fourteenth International Conference on Grey Literature - Rome, 2012
Graphs ofContent Models
Graphs ofData Objects
Compliant to
DLSdocumentmodelimplementation
FEDORA
OAIzer
Entity Graph
OAI view
represents
View Interpreter
OAI-OREexporter
OAI-PMHpublisher
PHASE 1: ENTITY GRAPH
Entity Graph: Graph representation of the document model
•Created exploiting information about Content Models
•Graph nodes represent Content Models
•Properties of a node represent the datastreams definedby the Content Model
•Edges between nodes represent the relationshipsdefined by the Content Models
Fourteenth International Conference on Grey Literature - Rome, 2012
ds:DC
ds:ART
name:CM_article
ds:DC
ds:DATA
GENERATES
USED_BY
GENERATED_BY
name:CM_data
USES
ds:DDI
CM_article
ds: ART,PDFds: DC, XML
CM_data
ds: DATA, bin
ds: DC, XML
ds: DDI, XML
USED_BY
GENERATED_BY
GENERATES
USES
PHASE 2: DEFINITION OF THEOAI VIEW
Fourteenth International Conference on Grey Literature - Rome, 2012
OAI View: Tree representation of the structure of thecompound objects to export
•Sub graph of the entity graph with entities andrelationships to include in the compound object
•Ex. The DATA datastream of CM_data is excluded
•The root node is the entry point of the OAI view
ds:DC
name:CM_article
ds:DC
USES
name:CM_data
ds:DDI
name:CM_article
ds:DC
GENERATED_BY
Fourteenth International Conference on Grey Literature - Rome, 2012
PHASE 3.1: INTERPRETATION OFTHE OAI VIEW FOR OAI-PMH
ds:DC
ID: Art2
ds:DC
USES
ID: Data1
ds:DDI
Set View
Data TransformationRule (XSLT):OaizerXML -> MF1
ItemInstance_View_2
....
....
....
....
....
OAIZER-XMLXml Serialization ofthe Instance View
ItemInstance_View_1
•DC
•OAIZER-XML
•MF1
OAI-PMHViewInterpreter
Instance View: createdby navigating thegraph of Data Objectsaccording to the pathsin the view
•DC
•OAIZER-XML
•MF1
PHASE 3.2: INTERPRETATIONOF THE OAI VIEW FOR OAI-ORE
Fourteenth International Conference on Grey Literature - Rome, 2012
ds:DC
Art2
Data1
ds:DC
USES
Art1
GENERATED_BY
ds:DDI
ds:DC
GENERATED_BY
http://<server>/oaizer/Art1/OAIZER-XML
USES
proxyFor
proxyIn
proxyFor
proxyIn
Aggr
proxyFor
proxyIn
Legend:
Aggregation
Aggregated resource
Proxy
ore:aggregates relation
OAI-ORE ViewInterpreter
http://<server>/oaizer/Data1/OAIZER-XML
http://<server>/oaizer/Art2/OAIZER-XML
FEDORA-OAIZER
Fourteenth International Conference on Grey Literature - Rome, 2012
PMH Item
PMH MetadataRecords
PMH MetadataFormat
OAIzer
OAI View Instance
Generated from OAIView Instance
DC, OAIzerXML, anyother format requireappropriate XSLT
ORE Aggregation
ORE AggregatedResources
ORE Proxy
OAI View Instance
Fedora Data Objectsin the OAI viewinstance
Fedora Data Objectsin the OAI viewinstance
Relationships betweenAggregated Resources
Compound Object Boundaries
YES
OAI View
(property and navigational criteria)
CONCLUSIONS
Don’t adapt your document model for the exports,adapt the exports to your document model!
•Customized, domain-dependent exports ofcompound objects
•Future work:
•Better graphical support for the definition of viewsin case of entity graphs with cycles
•Implementations for different back-ends
•Integration of DB-OAIzer with
Fourteenth International Conference on Grey Literature - Rome, 2012
