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GLOBE – OER AsiaSeminar
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http://www.slideshare.net/xaoch
Descargue esta presentación
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Agenda
• What is GLOBE?• GLOBE Architecture
– LOM– OAI-PMH– SQI
• GLOBE Metadata• ARIADNE Tools
– Repository– Registry– Harvester– Validation– Finder
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GLOBE
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http://www.globe-info.org/
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Large-Scale: 630.000+ instances
Real-World: being used and created
Heterogeneous: 7 networks of LORs4 continents
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GLOBE Architecture
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Federation of Federations
• What it does:– Provide a common way interchange description of
learning resources• What it does not do:
– Determine how each federation works– Determine how that description is stored internally at
each federation– Provide tools for federation users
• What it will do:– Provide a distributed registry of Federations
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To Federate Federations
• Resource Description:– Learning Object Metadata
• Federated Query:– Simple Query Interface
• Metadata Harvesting:– OAI – Protocol for Metadata Harvesting
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Resource Description
• Many ways to describe resources– Dublin Core– MARC– Learning Object Metadata– MPEG-7– etc…
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Learning Object Metadata
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Remember…
• GLOBE needs you to share LOM• Not to use LOM as your internal storage
method• Here is where Transformation Services could
be useful
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How to share: Two Approaches
• Federated Query– The Query is distributed to all the repositories– Each repository answers – The responses are collected and presented
• Harvesting– The metadata is harvested and stored centrally– The query is executed over the collected metadata– The response is presented
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<results>
</results>
Query
MELT repository-
Federated Search
Ariadne Federated Search Engine
Federated Search Invocation QueryQueryQueryQuery
<lom>…</..><lom>…</..>
<results> <lom>..</lom> <lom>..</lom> <lom>..</lom>…
</results>
<lom>…</..>
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Harvesting
CentralRepository
Repository
RepositoryRepository
Repository
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Harvesting
CentralRepository
Repository
RepositoryRepository
Repository
Harvest
Harvest
Harvest
Harvest
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Harvesting
CentralRepository
Repository
Repository
Repository
Repository
QueryQueryQueryQueryQuery
<results> <lom>..</lom> <lom>..</lom> <lom>..</lom>…
</results>
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Federated Query vs Harvesting
Federated Query Harvesting
Content (Objects) Distributed Distributed
Object Presentation Data provider Data provider
Searching is Distributed Centralized
Search done by Data provider Service provider
Metadata searched is Up to date Harvested version
Semantic Mapping At searching At metadata delivery
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Federated Query vs Harvesting
• Federated Query problems– Does not scale to large number of repositories– Advanced sorting/ranking very difficult– Problem with Repository uptime
• Harvesting problems– Need for a centralized (large) repository– Single point of failure
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GLOBE Solution: Hybrid Architecture
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How OAI works
• OAI “VERBS”– Identify – ListMetadataFormats– GetRecord– ListIdentifiers– ListRecords– ListSets
HARVESTER
REPOSITORY
OAI OAI
Service Provider Metadata Provider
HTTP Request
HTTP Response
(OAI Verb)
(Valid XML)
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Verbs• Identify • ListMetadataFormats• GetRecord• ListRecords• ListIdentifiers• ListSets
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GetRecord
• Purpose– Returns the metadata for a single item in the form
of an OAI record• Parameters
– identifier – unique id for item (R)– metadataPrefix – metadata format for the record
(R)
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ListRecords
• Purpose– Retrieves metadata records for multiple items
• Parameters– from – start date (O)
• greater than or equal to
– until – end date (O)• less than or equal to
– set – set to harvest from (O)– resumptionToken – flow control mechanism (X)– metadataPrefix – metadata format (R)
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ListRecords – from untilhttp://localhost:8080/oaicat/OAIHandler?verb=ListRecords&from=1999-01-15&until=2005-12-31&metadataPrefix=oai_lom…
UTCdatetimeDates and times are uniformly encoded using ISO8601 and are expressed in UTC throughout the protocol. When time is included, the special UTC designator ("Z") must be used. UTC is implied for dates although no timezone designator is specified. For example, 1957-03-20T20:30:00Z is UTC 8:30:00 PM on March 20th 1957. UTCdatetime is used in both protocol requests and protocol replies, in the way described in the following sections.
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ListIdentifiers• Purpose
– List headers for all items corresponding to the specified parameters• Parameters
– from – start date (O)– until – end date (O)– set – set to harvest from (O)– metadataPrefix – metadata format to list identifiers for (R)– resumptionToken – flow control mechanism (X)
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ListSets
• Purpose– Provide a listing of sets in which records may be
organized (may be hierarchical, overlapping, or flat)
• Parameters– None
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More Info
• http://ariadne.cs.kuleuven.be/lomi/index.php/Setting_Up_OAI-PMH
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Simple Query Interface
For example:EDUTELLA
For example:
Simple Query Interface Component
Learning Repository B(Target)
LearningObjectMetadata
Common Query Language & Schema
Results in Local Schema
Results in Common Schema
Local Query Language & Schema
Simple Query Interface Component
Learning Repository A
(Source)
Wrapper
Wrapper
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SQI is not...
SQI is ...
... a specification of the Query Service
... a specification of the Query Language
... a specification of the Results Format
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Overview of SQI Methods
• Query Configuration setQueryLanguage (may) setResultsFormat (may) setMaxQueryResults (must) setMaxDuration (may)
• Synchronous Query Interface setResultsSetSize (may) synchronousQuery (must) getTotalResultsCount (must) getAdditionalQueryResults (may)
Asynchronous Query Interface asynchronousQuery (must) setSourceLocation (may) queryResultsListener (must)
Results Management getResourceDescription (may)
Session Management createSession (may) createAnonymousSession (must)
destroySession (must)
Must be implemented May be-OptionalCould be Synch/Asynch/Both
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How: Synchronous
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How: Asynchronous
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GLOBE Metadata
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GLOBE Havestable Size
ARIADNE LRE KERIS ISKME LACLO OUJ LORNET1,000
10,000
100,000
1,000,000
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Metadata Record Size
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Metadata Record Size
≈ 5 Kb
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LOM Elements Use
What parts of LOM are used anyway?
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TitleIdentifierLanguage
DescriptionKeyword
LearningObjectKindStructure
AggregationLevelCoverage
Contribute.RoleContribute.Entity
Contribute.DateStatus
VersionIdentifier
Contribute.RoleContribute.Entity
Contribute.DateLanguage
MetadataSchemaLocation
FormatRequirement
SizeDuration
Requirement.OrCompositeLearningResourceType
TypicalAgeRangeIntendedEndUser
ContextInteractivityTypeInteractivityLevel
LanguageDifficulty
CopyrightCost
DescriptionKind
Resource.IdentifierResource.Description
TaxonPathPurpose
Taxon
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
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TitleIdentifierLanguage
DescriptionKeyword
LearningObjectKindStructure
AggregationLevelCoverage
Contribute.RoleContribute.Entity
Contribute.DateStatus
VersionIdentifier
Contribute.RoleContribute.Entity
Contribute.DateLanguage
MetadataSchemaLocation
FormatRequirement
SizeDuration
Requirement.OrCompositeLearningResourceType
TypicalAgeRangeIntendedEndUser
ContextInteractivityTypeInteractivityLevel
LanguageDifficulty
CopyrightCost
DescriptionKind
Resource.IdentifierResource.Description
TaxonPathPurpose
Taxon
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
G.TitleG.IdentifierG.LanguageG.DescriptionG.KeywordL.ContributionRoleL.ContirubtionEntityM.IdentifierM.ContributorRoleM.ContributorEntityM.ContributorDateT.LocationT.FormatE.LearningResourceTypeR.CopyrightR.CostR.DescriptionC.TaxonPathC.PurposeC.Taxon
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G.TitleG.IdentifierG.LanguageG.DescriptionG.KeywordL.ContributionRoleL.ContirubtionEntityM.IdentifierM.ContributorRoleM.ContributorEntityM.ContributorDateT.LocationT.FormatE.LearningResourceTypeR.CopyrightR.CostR.DescriptionC.TaxonPathC.PurposeC.Taxon
CreatorIdentifierTitleDateTypeSubjectDescription
LOM
DC
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G.TitleG.IdentifierG.LanguageG.DescriptionG.KeywordL.ContributionRoleL.ContirubtionEntityM.IdentifierM.ContributorRoleM.ContributorEntityM.ContributorDateT.LocationT.FormatE.LearningResourceTypeR.CopyrightR.CostR.DescriptionC.TaxonPathC.PurposeC.Taxon
CreatorIdentifierTitleDateTypeSubjectDescription
LOM
DC
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LOM uses 20 out of 50 elements
But captures more information than DC
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Educational Section
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4 out of 11 Educational elements
Community dependent
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LOM Vocabulary Usage
What is stored on LOM?
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Educational.Context
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Right.Cost
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Rights.Copyrights
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LOM XMLValidation Analysis
Is it an interoperability standard?
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LOM validation
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Most common errors (loose)
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LOM XML loose is widely implemented
LOM XML strict is not
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Good structural interoperability
Although the value space is not clear
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vCard causes 68% errors
LOM developers hate vCard
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LOM Metadata Quality Analysis
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Diversity of Vocabulary usage
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Diversity of Vocabulary usage
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Diversity of Vocabulary usage
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Quality of Textual Descriptions
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Quality of Textual Descriptions
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Quality of Textual Descriptions
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Quality of Textual Descriptions
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There must be a QA process
That is true for bothautomatic and manual metadata
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GLOBE Application Profile
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ARIADNE Tools
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Installation Instructions
http://goo.gl/J4kZ4j
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Repository
• Metadata and object store• Query through:
– Simple Query Interface (SQI) specification– REST JSON Interface (not standard)
• Publication through: – Simple Publishing Interface (SPI) specification
• Harvestable trough:– Open Archives Initiative Protocol for Metadata
Harvesting (OAI-PMH).
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Finder
• Web interface to query Repository• It is very simple, just html+javascript• Can be added to any web page.
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Harvester
• The harvester is used to obtain metadata from other repositories
• It can run regularly checking for new metadata in registered repositories
• Can validate a target against a given standard (using the validation service)
• Can transform a target to another format (using the transformation service)
• Can add a unique identifier (using the Identifier Service)
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Validator
• Before obtaining metadata from a repository we can check if their metadata is valid
• ARIADNE Validator check a file or a complete repository (through OAI-PMH)
• It provides a report of the errors in the metadata
• It support diverse application profile.
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Registry
• In a federation of mid to large size, a way to keep the information about the individual repositories is needed
• ARIADNE has implemented a Registry to index the metadata about the repositories and their collections
• It is based in the same software than the repository
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Gracias / Thank you / Terima Kasih
Xavier [email protected]://ariadne.cti.espol.edu.ec/xavierTwitter: @xaoch