HowTo OAI-PMH

HowTo implement OAI-PMH in 5 steps

• 1. Join the community: Register to the 'OAI Implementers list' at the official OAI Homepage
• 2. Read the spec.: The Harvesting Protocol (version 2.0) specification together with Implementation Guidelines
• 3. Look at existing tools, rated above.
• 4. Implement DC model and test it: The official OAI Repository Explorer. Most important operations (called 'verbs') are Identify, ListMetadataFormats, ListRecords and GetRecord, perhaps initially without incremental harvesting (resumption process).
• 5. Extend it eventually with specific metadata models and respective XML formats.

Minimal OAI-PMH data provider implementation

Following are more specific guidelines for a minimal OAI-PMH implementation of a so called 'data provider' using only the mandatory 'unqualified' Dublin Core (DC):

• Only three operations (verbs) are needed: Identify, ListMetadataFormats and ListRecords.
• Following operations are not required (initially): ListIdentifiers, ListSets, GetRecord.
• No incremental harvesting (resumption process for ListXxx operations with more than 1000 records)
• No compression as defined in the OAI-PMH spec. (compression at lower http level still possible)
• Date granularity may be 'day' not seconds (YYYY-MM-DD)
• Keeping track of deleted records may not be supported (deletedRecord=no)
• The default data model supported is Dublin Core but this still needs some decisions and explanations (as shown below)

Dublin Core with considerations for GIS

Mandatory Dublin Core (DC) supported as data model is sufficient for a start but with specific semantics (e.g. coverage, relation) (see also example below):

• dc:description contains dct:abstract
• dc:coverage contains a lat/lon bounding box encoding as defined in http://georss.org/simple.html#Box (minx, miny, maxx, maxy: dc:coverage example for a Swiss Canton: 7.30676 47.0585 8.10371 47.5371)
• dc:date means in fact dct:modified
• dc:relation is filled in with dclite4g:onLineSrc. If dc:type='service' dct:hasPart can be derived from GetCapabilities.

OAI implementations

• Geometa-Editor
• GeoShop, Fa. infoGrips GmbH, Zurich, Switzerland (C, Java)
• GeoNetwork, open source, rel. 2.2 (GPL, Java)