Globe seminar

GLOBE – OER AsiaSeminar

http://www.slideshare.net/xaoch

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Agenda

• What is GLOBE?• GLOBE Architecture

– LOM– OAI-PMH– SQI

• GLOBE Metadata• ARIADNE Tools

– Repository– Registry– Harvester– Validation– Finder

GLOBE

http://www.globe-info.org/

Large-Scale: 630.000+ instances

Real-World: being used and created

Heterogeneous: 7 networks of LORs4 continents

GLOBE Architecture

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

To Federate Federations

• Resource Description:– Learning Object Metadata

• Federated Query:– Simple Query Interface

• Metadata Harvesting:– OAI – Protocol for Metadata Harvesting

Resource Description

• Many ways to describe resources– Dublin Core– MARC– Learning Object Metadata– MPEG-7– etc…

Learning Object Metadata

Remember…

• GLOBE needs you to share LOM• Not to use LOM as your internal storage

method• Here is where Transformation Services could

be useful

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

<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>…</..>

Harvesting

CentralRepository

Repository

RepositoryRepository

Repository

Harvesting

CentralRepository

Repository

RepositoryRepository

Repository

Harvest

Harvest

Harvest

Harvest

Harvesting

CentralRepository

Repository

Repository

Repository

Repository

QueryQueryQueryQueryQuery

<results> <lom>..</lom> <lom>..</lom> <lom>..</lom>…

</results>

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

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

GLOBE Solution: Hybrid Architecture

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)

Verbs• Identify • ListMetadataFormats• GetRecord• ListRecords• ListIdentifiers• ListSets

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)

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)

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.

http://www.w3.org/TR/NOTE-datetime

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)

ListSets

• Purpose– Provide a listing of sets in which records may be

organized (may be hierarchical, overlapping, or flat)

• Parameters– None

More Info

• http://ariadne.cs.kuleuven.be/lomi/index.php/Setting_Up_OAI-PMH

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

SQI is not...

SQI is ...

... a specification of the Query Service

... a specification of the Query Language

... a specification of the Results Format

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

How: Synchronous

How: Asynchronous

GLOBE Metadata

GLOBE Havestable Size

ARIADNE LRE KERIS ISKME LACLO OUJ LORNET1,000

10,000

100,000

1,000,000

Metadata Record Size

Metadata Record Size

≈ 5 Kb

LOM Elements Use

What parts of LOM are used anyway?

TitleIdentifierLanguage

DescriptionKeyword

LearningObjectKindStructure

AggregationLevelCoverage

Contribute.RoleContribute.Entity

Contribute.DateStatus

VersionIdentifier


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%

TitleIdentifierLanguage

DescriptionKeyword

LearningObjectKindStructure

AggregationLevelCoverage


Contribute.DateStatus

VersionIdentifier


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


CreatorIdentifierTitleDateTypeSubjectDescription

LOM

DC


CreatorIdentifierTitleDateTypeSubjectDescription

LOM

DC

LOM uses 20 out of 50 elements

But captures more information than DC

Educational Section

4 out of 11 Educational elements

Community dependent

LOM Vocabulary Usage

What is stored on LOM?

Educational.Context

Right.Cost

Rights.Copyrights

LOM XMLValidation Analysis

Is it an interoperability standard?

LOM validation

Most common errors (loose)

LOM XML loose is widely implemented

LOM XML strict is not

Good structural interoperability

Although the value space is not clear

vCard causes 68% errors

LOM developers hate vCard

LOM Metadata Quality Analysis

Diversity of Vocabulary usage



Quality of Textual Descriptions




There must be a QA process

That is true for bothautomatic and manual metadata

GLOBE Application Profile

ARIADNE Tools

Installation Instructions

http://goo.gl/J4kZ4j

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).

Finder

• Web interface to query Repository• It is very simple, just html+javascript• Can be added to any web page.

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)

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.

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

Gracias / Thank you / Terima Kasih

Xavier [email protected]://ariadne.cti.espol.edu.ec/xavierTwitter: @xaoch

Technology

Globe seminar