1. Open Archives Initiative Protocol for Metadata Harvesting

2. Collections in isolation  Some thoughts  A wonderful collection is of limited use if it is not well known.  Very redundant collections are often wasteful

3. Virtual collections  Some collections do not contain actual materials, only information about materials and links to the home site.  How do these virtual collections get the information about other collections? How do they stay up to date?  --> The Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH)

4. OAI - PMH  A protocol -- that is just an agreement to exchange messages and interpret them according to strict rules.  Metadata -- data about the data -- information about the material in the collection  Harvesting -- gathering in the desired part of the collection for further use

5. The protocol  See http://www.openarchives.org/OAI/openarchivesprotocol.html  Two sides - the repository and the harvestor  The repository (data providers)  Prepares the required metadata  Responds to the harvester queries  Acts like a server - responding to queries when they come  The Harvester (data gatherer)  Gathers the metadata from the collections  Organizes the harvested metadata in a way to serve its purpose.  Acts like a client - requesting service when it needs it.

6. Resource, item, record  Resource: the actual content of the collection; the point of the digital library  Item: a part of the repository that generates the metadata.  Record: metadata in a specific format available for dissemination.  Encoded in XML  Unique identifier  Datestamp  setSpecµ  Optional status

7. Sets  Repositories may organize items into sets  Allows selective harvesting  Each node in a set organization has  setSpec  Set may be hierarchical. If so, the levels are separated by colons  setName  setDescription

8. Requests  Request embedded in an HTTP request  Valid OAI PMH Requests:  GetRecord  Identify  ListIdentifiers  ListMetadataFormats  ListRecords  ListSets

9. GetRecord  Required arguments  Identifier = unique identifier of an item whose record is requested  metadataPrefix = prefix part of the metadata record relevant to the requested item  This identifies the type of metadata applied to the record. Example = oai_dc (the OAI version of the Dublin Core -- standard 15 elements, no extension.)  Errors: badArgument, cannotDisseminateFormat, idDoesNotExist

10. Identify  No arguments  Requests information about the repository.  Response includes  repositoryName  BaseURL  protocolVersion  earliestDatestamp  deletedRecord (how does the repository handle deletions -- no, transient, persistent  Granularity (how finely can the datestamp be specified?)  adminEmail  compression (what schemes are supported)  description Optional

11. ListIdentifiers  Required Argument  metadataPrefix  Optional Arguments  from  until  set  Exclusive argument  resumptionToken (flow control token for resuming an incompleted previous ListIdentifiers request)  Errors: badArgument, badResumptionToken, cannotDisseminateFormat, noRecordsMatch, noSetHierarchy

12. ListMetadataFormats  Optional argument  identifier (if metadataformat is needed only for some particular item)  Errors - badArgument, idDoesNotExist, noMetadataFormats  Response includes both metadataPrefix and the associated schema

13. ListRecords  Required arguments  metadataPrefix - Only records for which the specified metadataPrefix applies should be returned  Optional arguments  from  until  set  Exclusive arguments  resumtpionToken

14. ListSets  Exclusive Argument  resumptionToken (used to continue a previous incomplete response to ListSets)  Errors - badArgument, badResumtpionToken, noSetHierarchy

15. Resources  Compliance testing - www.dlib.vt.edu/projects/OAI/repexp/repexp.html  OAI PMH - www.openarchives.org/OAI/openarchivesprotocol.html  Implementation Guidelines www.openarchives.org/OAI/2.0/guidelines.htm