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OAI 2.0 is a Java implementation of an OAI-PMH data provider interface developed by Lyncode that uses XOAI, an OAI-PMH Java Library, http://www.lyncode.com/dspace/addons/xoai/doc/XOAI_en.pdf.

Why OAI 2.0?

Projects like OpenAIRE, and Driver have specific metadata requirements (to the published content through the OAI-PMH interface). As the OAI-PMH protocol doesn't establish any frame to these specifics, OAI 2.0 can, in a simple way, have more than one instance of an OAI interface (feature provided by the XOAI core library) so one could define an interface for each project. That is the main purpose, although, OAI 2.0 allows much more than that.

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With this these ingredients it is possible to build a robust solution that fulfills all requirements of Driver, OpenAIRE and also other project-specific requirements. As shown in Figure 1, with contexts one could select a subset of all available items in the data source. So when entering the OpenAIRE context, all OAI-PMH request will be restricted to that subset of items.

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Configuration

Basic Configuration

Configuration File:

[dspace]/config/modules/oai.cfg

Property:

storage

Example Value:

storage = solr

Information Note:

This allows to choose the OAI data source between solr and database

Property:

solr.url

Example Value:

solr.url = ${default.solr.server}/oai

Informational Note:

Solr Server location

Property:

identifier.prefix

Example Value:

identifier.prefix = ${dspace.hostname}

Informational Note:

OAI persistent identifier prefix. Format - oai:PREFIX:HANDLE

Property:

config.dir

Example Value:

config.dir = ${dspace.dir}/config/crosswalks/oai

Informational Note:

Configuration directory, used by XOAI (core library). Contains xoai.xml, metadata format XSLTs and transformer XSLTs.

Property:

cache.dir

Example Value:

cache.dir = ${dspace.dir}/var/oai

Informational Note:

Directory to store runtime generated files (for caching purposes).

Advanced Configuration

OAI 2.0 allows you to configure following advanced options:

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Code Block
<Format id="[IDENTIFIER]">
  <Prefix>[PREFIX]</Prefix>
  <XSLT>metadataFormats/[XSLT]</XSLT>
  <Namespace>[NAMESPACE]</Namespace>
  <SchemaLocation>[SCHEMA_LOCATION]</SchemaLocation>
</Format>

where:

Parameter

Description

IDENTIFIER

The identifier used within context configurations to reference this specific format, must be unique within all Metadata Formats available.

PREFIX

The prefix used in OAI interface (metadataPrefix=PREFIX).

XSLT

The name of the XSLT file within [dspace]/config/crosswalks/oai/metadataFormats directory

NAMESPACE

XML Default Namespace of the created Schema

SCHEMA_LOCATION

URI Location of the XSD of the created Schema

NOTE: Changes in [dspace]/config/crosswalks/oai/xoai.xml requires reloading/restarting the servlet container.

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Therefore exposing any DSpace metadata field in any OAI format is just a matter of modifying the corresponding output format stylesheet (This assumes the general knowledge of how XSLT works. For a tutorial, see e.g. http://www.w3schools.com/xsl/).

For example, if you have a DC field "local.note.librarian" that you want to expose in oai_dc as <dc:note> (please note that this is not a valid DC field and thus breaks compatibility), then edit oai_dc.xsl and add the following lines just above the closing tag </oai_dc:dc>:

Code Block
languagexml
<xsl:for-each select="doc:metadata/doc:element[@name='local']/doc:element[@name='note']/doc:element/doc:element/doc:field[@name='librarian']">
    <dc:note><xsl:value-of select="." /></dc:note>
</xsl:for-each>

If you need to add/remove metadata fields, you're changing the output format. Therefore it is recommended to create a new If you need to add/remove metadata fields, you're changing the output format. Therefore it is recommended to create a new metadata format as a copy of the one you want to modify. This way the old format will remain available along with the new one and any upgrades to the original format during DSpace upgrades will not overwrite your customizations. If you need the format to have the same name as the original format (e.g. the default oai_dc format), you can create a new context in xoai.xsl containing your modified format with the original name, which will be available as /oai/context-name.

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Info
titleRelevant Links

Sanity check your OAI interface with the OAI Validator

There is a very useful validator for OAI interfaces available at http://validator.oaipmh.com, we urge you to use this validator to confirm your OAI interface is in fact usable.