The Clinical Journal of Obstetrics and Gynecology (CJOG) supports the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH), enabling global indexing services, libraries, aggregators, and open-access repositories to automatically harvest our article metadata. This page provides complete documentation of our OAI-PMH endpoint, supported metadata formats, recommended harvesting practices, and interoperability guidelines.

About OAI-PMH

OAI-PMH is an established standard for collecting, transferring, and synchronizing metadata between repositories. It facilitates large-scale harvesting of open-access scholarly content, ensuring long-term discoverability, interoperability, and integration across global knowledge infrastructures such as library systems, medical research indexes, academic search engines, and open-science platforms.

CJOG OAI-PMH Base URL

CJOG provides a fully functional OAI-PMH endpoint, accessible at:

http://obstetricgynecoljournal.com/index.php/cjog/oai

This endpoint allows metadata harvesters to retrieve article metadata in various standardized formats.

Supported Metadata Formats

CJOG supports multiple metadata formats through OAI-PMH to ensure compatibility with diverse indexing and repository systems.

Metadata Format	OAI Identifier	Description
Dublin Core (DC)	`oai_dc`	Standard unqualified Dublin Core format used by most general OA harvesters.
METS	`mets`	Metadata Encoding and Transmission Standard for structural and administrative metadata.
MODS	`mods`	Metadata Object Description Schema—commonly used by libraries for precise bibliographic information.
Crossref XML	`crossref`	Publisher-supplied Crossref-compatible metadata including DOIs, references, and ORCID links.
OAI-MARC	`marc`	Used by library systems around the world for bibliographic classification.
NLM JATS XML (if enabled)	`jats`	Journal Article Tag Suite for high-fidelity scholarly metadata, ideal for medical databases.

Example OAI-PMH Requests

Below are common queries harvesters use to extract metadata.

Identify Repository

http://obstetricgynecoljournal.com/index.php/cjog/oai?verb=Identify

List Metadata Formats

http://obstetricgynecoljournal.com/index.php/cjog/oai?verb=ListMetadataFormats

List All Records (Dublin Core)

http://obstetricgynecoljournal.com/index.php/cjog/oai?verb=ListRecords&metadataPrefix=oai_dc

Retrieve a Single Record

http://obstetricgynecoljournal.com/index.php/cjog/oai?verb=GetRecord&identifier=oai:cjog:articleID&metadataPrefix=oai_dc

Replace articleID with the numeric identifier provided by the system.

Harvesting Frequency Recommendations

To optimize server performance while maintaining metadata freshness, CJOG recommends:

Light harvesters (universities, libraries): every 24–72 hours.
Heavy aggregators (CORE, OpenAIRE, Semantic Scholar): every 12–24 hours.
Search engines (Google Scholar, Scilit): real-time or daily crawls.

Interoperability & Metadata Standards

CJOG adheres to internationally recognized metadata and interoperability standards:

Dublin Core (DC)
CROSSREF XML schema for DOIs
Schema.org JSON-LD for search engines
OpenURL linking for library systems
NLM / JATS XML for medical indexing
ORCID metadata linking for author identity consistency

OAI-PMH & Open Access Ecosystem

OAI-PMH functionality integrates with global open access infrastructure:

OpenAIRE – European open science network
CORE – global OA aggregator
OCLC/WorldCat – library system metadata sharing
Zenodo / Figshare – repository linking
Institutional repositories – automated metadata ingestion

Preservation Through OAI-PMH

OAI-PMH harvesting contributes significantly to CJOG’s long-term preservation strategy by ensuring:

Articles remain accessible even if primary servers change.
Backups exist across distributed global repositories.
Metadata is constantly synchronized with third-party archival platforms.

Metadata Completeness and Quality Assurance

CJOG conducts quarterly metadata audits to ensure:

All articles have DOIs and correct URL resolution.
Author names, ORCID iDs, affiliations, and abstracts are accurate.
Reference lists follow Crossref linking standards.
XML validation for JATS, Crossref, and Dublin Core.

OAI-PMH Error Handling

Common OAI-PMH errors and resolutions:

Error	Cause	Solution
`badArgument`	Invalid or missing verb/parameter.	Check syntax and include required parameters.
`badVerb`	Unsupported verb.	Use only standard verbs such as Identify, ListRecords, ListSets.
`idDoesNotExist`	Incorrect record identifier.	Verify the record identifier from platform.
`noRecordsMatch`	No records found for given criteria.	Adjust date ranges or prefix selection.

OAI Sets (If Enabled)

In OJS-based systems, OAI-PMH “sets” allow grouping of records by:

Journal sections
Article types (Research, Case Reports, Reviews…)
Volumes and issues
Special issues

If CJOG enables sets, harvesters may request:

?verb=ListSets

Best Practices for Harvesters

To ensure smooth integration:

Respect crawl delays and server load considerations.
Use compressed HTTP responses (gzip).
Harvest incrementally using “from” and “until” parameters.
Store identifiers for delta updating.

Contact for Technical Support

For metadata harvesting assistance or OAI-PMH troubleshooting:

Email: [email protected]
Publisher: Heighten Science Publications Inc.
Location: 138 Regina Dr, East Windsor, CT 06088, USA