Globe seminar
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Information on how GLOBE operates and how ARIADNE Toolset is put together
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Globe seminar
- 1. GLOBE – OER Asia Seminar
- 3. Agenda • What is GLOBE? • GLOBE Architecture – LOM – OAI-PMH – SQI • GLOBE Metadata • ARIADNE Tools – Repository – Registry – Harvester – Validation – Finder
- 4. GLOBE
- 6. Large-Scale: 630.000+ instances Real-World: being used and created Heterogeneous: 7 networks of LORs 4 continents
- 8. 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
- 10. To Federate Federations • Resource Description: – Learning Object Metadata • Federated Query: – Simple Query Interface • Metadata Harvesting: – OAI – Protocol for Metadata Harvesting
- 11. Resource Description • Many ways to describe resources – Dublin Core – MARC – Learning Object Metadata – MPEG-7 – etc…
- 13. Remember… • GLOBE needs you to share LOM • Not to use LOM as your internal storage method • Here is where Transformation Services could be useful
- 14. 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
- 15. <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>…</..>
- 19. 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
- 20. 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
- 21. GLOBE Solution: Hybrid Architecture
- 22. How OAI works • OAI “VERBS” – Identify – ListMetadataFormats – GetRecord – ListIdentifiers – ListRecords – ListSets H A R V E S T E R R E P O S I T O R Y OAI OAI Service Provider Metadata Provider HTTP Request HTTP Response (OAI Verb) (Valid XML)
- 23. Verbs • Identify • ListMetadataFormats • GetRecord • ListRecords • ListIdentifiers • ListSets
- 24. 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)
- 25. 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)
- 26. ListRecords – from until http://localhost:8080/oaicat/OAIHandler?verb=ListRecords& from=1999-01-15&until=2005-12-31&metadataPrefix=oai_lom… UTCdatetime Dates 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.
- 27. 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)
- 28. ListSets • Purpose – Provide a listing of sets in which records may be organized (may be hierarchical, overlapping, or flat) • Parameters – None
- 30. Simple Query Interface For example: EDUTELLA For example: Simple Query Interface Component Learning Repository B (Target) Learning Object Metadata 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
- 31. SQI is not... SQI is ... ... a specification of the Query Service ... a specification of the Query Language ... a specification of the Results Format
- 32. 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-Optional Could be Synch/Asynch/Both
- 33. How: Synchronous
- 35. GLOBE Metadata
- 36. GLOBE Havestable Size 1 10 100 1,000 10,000 100,000 1,000,000 ARIADNE LRE KERIS ISKME LACLO OUJ LORNET
- 38. Metadata Record Size ≈ 5 Kb
- 39. LOM Elements Use What parts of LOM are used anyway?
- 40. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Title Identifier Language Description Keyword LearningObjectKind Structure AggregationLevel Coverage Contribute.Role Contribute.Entity Contribute.Date Status Version Identifier Contribute.Role Contribute.Entity Contribute.Date Language MetadataSchema Location Format Requirement Size Duration Requirement.OrComposite LearningResourceType TypicalAgeRange IntendedEndUser Context InteractivityType InteractivityLevel Language Difficulty Copyright Cost Description Kind Resource.Identifier Resource.Description TaxonPath Purpose Taxon
- 41. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Title Identifier Language Description Keyword LearningObjectKind Structure AggregationLevel Coverage Contribute.Role Contribute.Entity Contribute.Date Status Version Identifier Contribute.Role Contribute.Entity Contribute.Date Language MetadataSchema Location Format Requirement Size Duration Requirement.OrComposite LearningResourceType TypicalAgeRange IntendedEndUser Context InteractivityType InteractivityLevel Language Difficulty Copyright Cost Description Kind Resource.Identifier Resource.Description TaxonPath Purpose Taxon G.Title G.Identifier G.Language G.Description G.Keyword L.ContributionRole L.ContirubtionEntity M.Identifier M.ContributorRole M.ContributorEntity M.ContributorDate T.Location T.Format E.LearningResourceType R.Copyright R.Cost R.Description C.TaxonPath C.Purpose C.Taxon
- 44. LOM uses 20 out of 50 elements But captures more information than DC
- 46. 4 out of 11 Educational elements Community dependent
- 47. LOM Vocabulary Usage What is stored on LOM?
- 49. Right.Cost
- 51. LOM XML Validation Analysis Is it an interoperability standard?
- 52. LOM validation
- 53. Most common errors (loose)
- 54. LOM XML loose is widely implemented LOM XML strict is not
- 55. Good structural interoperability Although the value space is not clear
- 56. vCard causes 68% errors LOM developers hate vCard
- 57. LOM Metadata Quality Analysis
- 58. Diversity of Vocabulary usage
- 59. Diversity of Vocabulary usage
- 60. Diversity of Vocabulary usage
- 61. Quality of Textual Descriptions
- 62. Quality of Textual Descriptions
- 63. Quality of Textual Descriptions
- 64. Quality of Textual Descriptions
- 65. There must be a QA process That is true for both automatic and manual metadata
- 67. ARIADNE Tools
- 70. 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).
- 71. Finder • Web interface to query Repository • It is very simple, just html+javascript • Can be added to any web page.
- 72. 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)
- 73. 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.
- 74. 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
- 75. Gracias / Thank you / Terima Kasih Xavier Ochoa xavier@cti.espol.edu.ec http://ariadne.cti.espol.edu.ec/xavier Twitter: @xaoch