XML Tagging Specifications

Minimum XML Requirements

All XML supplied to PMC is required to meet the following minimum requirements:

  1. It must conform to an acceptable journal article DTD. If you plan on submitting articles in using something other than the JATS or NLM Journal Publishing Tag Sets, please contact PMC at pmcapplication@ncbi.nlm.nih.gov prior to submitting any files.
  2. It must parse according to its DTD. PMC validates data using the PUBLIC ID in the DOCTYPE declaration in each source file.

    NOTE: If you are using the JATS or NLM Journal Publishing Tag Sets, PMC strongly suggests that you tag your articles so that they conform to PMC Style. You can use the Online PMC Style Checker or download a version of the Style Checker that can be run locally to confirm that any JATS or NLM XML file conforms to PMC Style. In addition, you may upload your articles to the PMC Article Previewer, which uses the same processes that are used during PMC production. This allows you to preview an article as it would appear in PMC.

  3. Regardless of the XML DTD used, the following metadata information must be present and tagged with correct values in every XML file:
    • Journal ISSN or other unique Journal ID
    • Journal Publisher
    • Copyright statement (if applicable)
    • License statement (if applicable)
    • Volume
    • Issue number (if applicable)
    • Pagination/article sequence number
    • Issue-based or Article-based publication dates

    NOTE: Articles submitted to PMC must contain publication dates that accurately reflect the journal’s publication model, following these general guidelines for publication date tagging

Additional XML Tagging Guidance

In addition to the minimum requirements above, below is guidance on a number of XML tagging issues that arise commonly in articles in PMC.

Release Delays or Embargoes


  • A release delay or embargo is the amount of elapsed time after an article publication date that PMC waits to release an article to the public.

Details on how to tag release delays using a processing instruction for PMC in the JATS or NLM DTD are included in the PMC Tagging Guidelines in the Release Delay Processing Instructions section.

PMC handling of articles with no specified released delay in the XML

The default date for the release of articles received with no release delay tagging in the XML is the publication date plus the embargo specified by the publisher’s agreement with PMC for the specific journal.

Tagging articles in the same journal with different release delays

Specify the release delay at the article level with a processing instruction. (Details on how to tag release delays using a processing instruction for PMC in the JATS or NLM DTD are included in the PMC Tagging Guidelines in the Release Delay Processing Instructions section.) Articles without a release delay explicitly tagged in the article XML will be released based on the default embargo set by the publisher’s agreement with PMC for that journal.

Tagging a single article with multiple release requirements based on differing author obligations

Provide the shortest applicable release delay in the XML file. If PMC receives a single article file with more than one release delay specified, release will occur based on the shortest release delay.

File packaging for a set of articles or a complete issue from one journal with differing release delays and/or access conditions

There is no need to separate articles from a single journal or issue into individual deliveries based on differences in release or access conditions. Tagging of this information is at the article level, not the delivery level.

Open Access and License Statements


  • A license is a statement which specifies copyright permission granted for an article.
  • An open access (OA) article, in the context of PMC, is an article that is published with a Creative Commons license or a similar license that allows any user to redistribute the article without requesting permission from the copyright holder. Additionally, this license may allow or prohibit the creation and distribution of derivative works or modified versions of the article, and/or may limit reuse and redistribution to non-commercial purposes only.

An open access article, in the context of PMC, is NOT simply an article that is freely available at the time of publication.

The following conditions apply to all OA articles in PMC:

  • The applicable license will be clearly indicated in both the XML and PDF versions of each OA article. The license data in the XML must conform to PMC’s guidelines for recording the terms of a license. See License Tagging Information below.
  • PMC will include the content (full-text XML and other files) for all OA articles in PMC's Open Access subset (“OA subset”).
  • Content for articles in the OA subset will be freely available to users for downloading via the PMC OAI (Open Archives Initiative) service, the PMC FTP service, and similar services that allow automated downloading of articles.
  • Reuse or redistribution by PMC users of content that is in the OA subset will be subject only to proper attribution of the original source and authorship, and to the license included in a particular article.

License Tagging Information

Any article that is to be open access must indicate that explicitly in the source XML file. For content that is supplied in the JATS or NLM Journal Publishing Tag Set, see the license tagging guidelines for detailed tagging information and examples.

For content supplied to PMC in a form other than the JATS or NLM Journal Publishing Tag Set, the guidelines are:

  1. Include a precise summary license statement in the source XML file.
  2. If you are referring to any standard license – such as a Creative Commons license – there should be a URI included for an unambiguous reference.

Grant and Funder Information

Explicit tagging of grant information is not required by PMC but may be supplied at the discretion of the publisher. The PMC Tagging Guidelines describe how to best capture funding information, including grant data and funding institutions.


PMC will not remove articles from its archive. However, in the event that a publisher discovers a serious problem with an article that exceeds the need for a simple correction or erratum notice, such as in cases of scientific misconduct, plagiarism, pervasive error or unsubstantiated data, then the journal must publish a notice of retraction. For more information see PMC’s policy on retractions.

A retracted article in PMC is marked boldly and includes a link to the retraction notice, as in this example. To tag the retraction, you should include specific citation information within the body of the article, as described in the PMC Tagging Guidelines.

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Last updated: Fri, 09 Dec 2011