OAI Protocol for Metadata Harvesting Tim Brody Intelligence, Agents, Multimedia Group University of Southampton OpCit – http://opcit.eprints.org/ www.ecs.soton.ac.uk BCS Metadata Meeting, London 29 th May 2002 (Many slides borrowed from Michael L. Nelson)
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OAI Protocol for Metadata Harvesting Tim Brody Intelligence, Agents, Multimedia Group University of Southampton OpCit – //opcit.eprints.org
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OAI Protocol for Metadata Harvesting
Tim BrodyIntelligence, Agents, Multimedia Group
University of SouthamptonOpCit – http://opcit.eprints.org/
• Goal: recurrent exchange of metadata about resources between systems
• Input:• OAI-PMH v.1.0 [01/01 – 09/02]• feedback on OAI-implementers• deliberations by OAI-tech [09/01 -]• alpha test group of OAI-PMH v.2.0 [03/02 -]
• low-barrier interoperability specification• metadata harvesting model: data provider / service
provider• metadata about resources • autonomous protocol• distinction between protocol and periphery
• community-specific extensions• HTTP based• XML responses• unqualified Dublin Core• stable (1.0 characterized as experimental)
OAI-PMH v.2.0 [06/2002]
OAI Data Model:
Resources / Items / Records
resource
all available metadata about David
item
Dublin Coremetadata
MARCmetadata
SPECTRUMmetadata records
item = identifier
record = identifier + metadata format + datestamp
Overview of OAI Verbs
Verb Function
Identify description of archive
ListMetadataFormats metadata formats supported by archive
ListSets sets defined by archive
ListIdentifiers OAI unique ids contained in archive
ListRecords listing of N records
GetRecord listing of a single record
archivalmetadata
harvestingverbs
most verbs take arguments: dates, sets, ids, metadata formatsand resumption token (for flow control)
<?xml version="1.0" encoding="UTF-8"?><OAI-PMH><responseDate>2002-0208T08:55:46Z</responseDate> <request>http://arXiv.org/oai2</request><error code=“badVerb”>ShowMe is not a valid OAI-PMH verb</error></OAI-PMH>
response with error
• Idempotency of resumptionToken: return same incomplete list when rT is re-issued• while no changes occur in the repo: strict• while changes occur in the repo: all items with unchanged
datestamp• new attributes for the resumptionToken:
• expirationDate• completeListSize• cursor
resumptionToken Flow-Control
• evolution
• from talking about OAI-PMH
• to talking about projects that use OAI-PMH
• to talking about projects and failing to mention they use OAI-PMH
• => OAI-PMH becomes part of the infrastructure
Adoption
• 49 registered repositories [11/2001]
• 65 registered repositories [03/2002]
• 77 registered repositories [05/2002]
• 5+ million records
• many unregistered repositories
• private implementations (e.g. RDN)
Data Providers (a.k.a. repositories)
• Arc: cross-searching of registered repositories [ http://arc.cs.odu.edu ]
• CiteBase: research literature search + citation ranking[ http://citebase.eprints.org ]
• OLAC: cross-searching of Language Archive Community repositories[ http://www.language-archives.org/index.html ]