Open Archive Initiative – Protocol for metadata Harvesting (OAI-PMH) Surinder Kumar Technical Director NIC, New Delhi

OAI-PMH The mission of the Open Archives Initiative (OAI) ( is to develop and promote “interoperability standards that aim to facilitate efficient dissemination of content.

OAI-PMH The OAI-PMH is based on a simple and powerful model “whereby repositories (data providers) make metadata... available via a well-defined protocol. The exposure of the metadata allows other organizations (service providers) to harvest it and then aggregate it, post-process it, and refine it with the goal of developing services that add value.

Background Has origins in ePrints (arXive, CogPrints), dating back to 1999 – actively seeking wider applicability – Nothing to do with OAIS Aims to “f acilitate the efficient dissemination of content” – free access to the archives (at least: metadata) – consistent interfaces for archives and service provider – low barrier protocol / effortless implementation (e.g., because based on HTTP, XML, DC) Now on version 2.0 (June 2002)

OAI-PMH: what’s it all about Service providers harvest metadata from data providers. Requests (HTTP) Metadata (XML) Data provider Metadata (+ resources) Harvester Service Provider Metadata “service” Adapted from OAI PMH

What can be requested (verb) Description of the archive (Identify) A list of metadata formats supported by the data provider (ListMetadataFormats) A list of sets provided (ListSets) A list of resource identifiers (ListIdentifiers) Many records (ListRecords) An individual record (GetRecord)

Example Requests archive.example.org/oaipmh?verb= ListRecords&metadataPrefix=oai_dc

Metadata Formats Metadata may be returned in any XML format Dublin Core is mandatory – OAI-PMH specifies the XML schema to use – No single DC element is mandatory Other element sets / bindings are optional – Qualified DC (e.g. RDN, NSDL) – MODS (LoC) – LOM (RDN-LTSN) – ODRL (JORUM ( I think) ) –...

Sets A grouping of items made to allow selective harvesting – E.g. all theses – E.g. the Engineering section – E.g. all resources from a given source Optional

List Records Harvester can ask for specific metadata format for – All available items – All items in a set – All records modified in given date range – (A single item — GetRecord) Data provider can return – All relevant records – Some relevant records + resumption token – An error code (no such set / metadata format)

Static Repositories Even lighter-weight specification for data providers with small and relatively static collections – E.g. the output from a conference Essentially an XML file available at a URL Accessed through a “static repository gateway” intermediary

Issues: complexity Providing data is easy Harvesting data is easy However Doing so may lead to complex workflow / policy issues – What do you do with the harvested metadata? – Do you modify the metadata you harvest? – If so, do you feed this back to the provider? – What if the provider changes a modified record? – Does a service provider disseminate via OAI?

Issues: uptake Lots of implementers, who have produced lots of useful support However Relatively little commercial uptake Relatively little support for harvesting rich metadata Relatively little support/consensus on sets

Issues: Harvesting resource (e.g. Full text) Nothing in OAI-PMH requires that full-text should be available for harvesting. – Resource may be physical or accessed controlled Nothing in OAI-PMH requires that information required for harvesting should be available. However in many cases OAI-PMH will provide the information required to harvest the resource.

Service Provider Arc: A Cross Archive Search Service From October 2000 Arc is an experimental research service that serves as a platform for demonstrating the scalability of the OAI-PMH and as a vehicle for providing access to OAI-compliant repositories through a unified search interface. Arc is the oldest federated search service based on the OAI-PMH.

OAISTER OAIster is a union catalog of digital resources. We provide access to these digital resources by "harvesting" their descriptive metadata (records) using OAI-PMH (the Open Archives Initiative Protocol for Metadata Harvesting).OAI-PMH

Service Providers Citebase May 2001 Citebase “allows researchers to search across free, full-text research literature eprint archives, with results ranked according to many criteria (e.g., citation impact), and then to navigate that literature using citation links and analysis.”

Contd… SAIL-eprints (Search, Alert, Impact and Link) April 2003 SAIL-eprints (Search, Alert, Impact and Link) is “an electronic open access service provider for finding scientific or technical documents, published or unpublished, in Chemistry, Physics, Engineering, Materials Sciences, Nanotechnologies, Microelectronics, Computer Sciences, Astronomy, Astrophysics, Earth Sciences, Meteorology, Oceanography,... [Agriculture], and related... [subjects].”

Resources Open Archives Initiative – – Spec, best practice guide and useful resources, mailing lists OAI for beginners – – Online tutorial OAI Repository Explorer – – Web interface for issuing OAI-PMH requests