OAI-PMH Dawn Petherick, University Web Services Team Manager, Information Services, University of Birmingham MIDESS Dissemination event, 4 th May 2007

What is OAI-PMH?  The OAI-Protocol for Metadata Harvesting (OAI- PMH) defines a mechanism for harvesting records containing metadata from repositories.  OAI-PMH uses the open standards HTTP (Hypertext Transport Protocol) and XML (eXtensible Markup Language) to enable access to metadata records.

How is it used?  A Data Provider maintains one or more repositories that support the OAI-PMH protocol.  A Service Provider issues OAI-PMH requests to data providers and uses the metadata as a basis for building value-added services. A Service Provider in this manner is "harvesting" the metadata exposed by Data Providers.  When a data provider has a large volume of records to return for a request it is able to return some of the records and a resumption token which can be used to retrieve the rest of the results.

OAI Requests  Service Providers make requests to Data Providers using one of six verbs: –Identify –ListMetadataFormats –ListSets –ListIdentifiers –ListRecords –GetRecord

Identify  Identify is used to gather information about the repository.  Uses no further arguments and the response should contain the following information: –base-URL of the repository –the OAI protocol version supported –the repository name – address of the repository administrator

ListMetadataFormats  This request will show the available metadata formats in the repository or optionally for a record.  Accepts one optional argument, identifier, used to limit the response to those metadata formats for a specific record.

ListMetadataFormats  The response from the data provider should include the following information for each metadata format supported: –metadata prefix –namespace (optional) –XSD (for validation)  If an identifier argument is given but no record exists, no metadata formats are returned.  There are no restrictions on the type of metadata that can be supported by the data provider, only that it must be returned as XML.

ListSets  ListSets is used to retrieve information on the sets of records that are available from the data provider, returned as: –setSpec –setName  The setsSpec keys returned by ListSets can be used with ListIdentifiers and ListRecords to limit the records that are returned.  The only argument that is accepted is a resumption token from a previous request.

ListIdentifiers  ListIdentifiers is used to request unique identifiers of records contained within the repository.  This request can optionally either have arguments (from, until & set) to limit the identifiers returned by the request by date & set or a resumption token to continue a previous request.  Deleted record identifiers are returned with a status of deleted.

ListRecords  ListRecords is used to harvest multiple records from a repository.  It has the same optional values to limit the records returned as ListIdentifiers but requires an additional argument, metadataPrefix which is used to determine the format that the metadata records will be returned in.  Deleted records are returned with a status of deleted and no metadata. Records not available with a specified metadataPrefix are returned with no metadata.

GetRecord  GetRecord is used to retrieve a single record from a data provider.  This verb accepts two mandatory arguments –metadataPrefix, discoverable from ListMetadataFormats –identifier, discoverable from ListIdentifiers  Deleted records are returned with a status of deleted and no metadata. Records not available with a specified metadataPrefix are returned with no metadata.

metadatPrefix=oai_dc  oai_dc is an xml representation of unqualified Dublin Core and is a reserved metadataPrefix in OAI-PMH.  It is mandatory for a repository to support oai_dc as a metadataPrefix as it considered to be the baseline for all data providers to be able expose metadata to service providers.

MIDESS OAI-PHM  During the MIDESS Project OAI-PMH has been evaluated as a possibility for sharing access to or discovery of collections between institutions.  Although the repositories can act as Data Providers, we have experienced problems as none of the repositories natively acts as a service provider (to process data harvested from other institutions)

MIDESS OAI-PMH  At the University of Birmingham we were able to create a workaround by creating a service provider client that harvested metadata from the other MIDESS data providers and create items for DSpace to ingest (using it’s import tools).

Further technical questions….  Contact Matt Martin, Digital Library Technical Analyst at or tel: