Entity Field Reference

All entities have:

  • extra: free-form JSON metadata

The "extra" field is an "escape hatch" to include extra fields not in the regular schema. It is intended to enable gradual evolution of the schema, as well as accommodating niche or field-specific content. Reasonable care should be taken with this extra metadata: don't include large text or binary fields, hundreds of fields, duplicate metadata, etc.


  • name (string, required): The title of the publication, as used in international indexing services. Eg, "Journal of Important Results". Not necessarily in the native language, but also not necessarily in English. Alternative titles (and translations) can be stored in "extra" metadata (see below)
  • container_type (string): eg, journal vs. conference vs. book series. Controlled vocabulary is TODO.
  • publisher (string): The name of the publishing organization. Eg, "Society of Curious Students".
  • issnl (string): an external identifier, with registration controlled by the ISSN organization. Registration is relatively inexpensive and easy to obtain (depending on world region), so almost all serial publications have one. The ISSN-L ("linking ISSN") is one of either the print ("ISSNp") or electronic ("ISSNe") identifiers for a serial publication; not all publications have both types of ISSN, but many do, which can cause confusion. The ISSN master list is not gratis/public, but the ISSN-L mapping is.
  • wikidata_qid (string): external linking identifier to a Wikidata entity.

extra Fields

  • abbrev (string): a commonly used abbreviation for the publication, as used in citations, following the ISO 4 standard. Eg, "Journal of Polymer Science Part A" -> "J. Polym. Sci. A"
  • coden (string): an external identifier, the CODEN code. 6 characters, all upper-case.
  • issnp (string): Print ISSN
  • issne (string): Electronic ISSN
  • default_license (string, slug): short name (eg, "CC-BY-SA") for the default/recommended license for works published in this container
  • original_name (string): native name (if name is translated)
  • platform (string): hosting platform: OJS, wordpress, scielo, etc
  • mimetypes (array of string): formats that this container publishes all works under (eg, 'application/pdf', 'text/html')
  • first_year (integer): first year of publication
  • last_year (integer): final year of publication (implies that container is no longer active)
  • languages (array of strings): ISO codes; the first entry is considered the "primary" language (if that makes sense)
  • country (string): ISO abbreviation (two characters) for the country this container is published in
  • aliases (array of strings): significant alternative names or abbreviations for this container (not just capitalization/punctuation)
  • region (string, slug): continent/world-region (vocabulary is TODO)
  • discipline (string, slug): highest-level subject aread (vocabulary is TODO)
  • urls (array of strings): known homepage URLs for this container (first in array is default)

Additional fields used in analytics and "curration" tracking:

  • doaj (object)
    • as_of (string, ISO datetime): datetime of most recent check; if not set, not actually in DOAJ
    • seal (bool): has DOAJ seal
    • work_level (bool): whether work-level publications are registered with DOAJ
    • archive (array of strings): preservation archives
  • road (object)
    • as_of (string, ISO datetime): datetime of most recent check; if not set, not actually in ROAD
  • kbart (object)
    • lockss, clockss, portico, jstor etc (object)
      • year_spans (array of arrays of integers (pairs)): year spans (inclusive) for which the given archive has preserved this container
      • volume_spans (array of arrays of integers (pairs)): volume spans (inclusive) for which the given archive has preserved this container
  • sherpa_romeo (object):
    • color (string): the SHERPA/RoMEO "color" of the publisher of this container
  • doi: TODO: include list of prefixes and which (if any) DOI registrar is used
  • dblp (object):
    • id (string)
  • ia (object): Internet Archive specific fields
    • sim (object): same format as kbart preservation above; coverage in microfilm collection
    • longtail (bool): is this considered a "long-tail" open access venue

For KBART and other "coverage" fields, we "over-count" on the assumption that works with "in-progress" status will soon actually be preserved. Elements of these arrays are either an integer (means that single year is preserved), or an array of length two (meaning everything between the two numbers (inclusive) is preserved).


  • display_name (string, required): Full name, as will be displayed in user interfaces. Eg, "Grace Hopper"
  • given_name (string): Also known as "first name". Eg, "Grace".
  • surname (string): Also known as "last name". Eg, "Hooper".
  • orcid (string): external identifier, as registered with ORCID.
  • wikidata_qid (string): external linking identifier to a Wikidata entity.

See also "Human Names" sub-section of style guide.


  • size (integer, positive, non-zero): Size of file in bytes. Eg: 1048576.
  • md5 (string): MD5 hash in lower-case hex. Eg: "d41efcc592d1e40ac13905377399eb9b".
  • sha1 (string): SHA-1 hash in lower-case hex. Not required, but the most-used of the hashes and should always be included. Eg: "f013d66c7f6817d08b7eb2a93e6d0440c1f3e7f8".
  • sha256: SHA-256 hash in lower-case hex. Eg: "a77e4c11a57f1d757fca5754a8f83b5d4ece49a2d28596889127c1a2f3f28832".
  • urls: An array of "typed" URLs. Order is not meaningful, and may not be preserved.
    • url (string, required): Eg: "https://example.edu/~frau/prcding.pdf".
    • rel (string, required): Eg: "webarchive".
  • mimetype (string): Format of the file. If XML, specific schema can be included after a +. Example: "application/pdf"
  • release_ids (array of string identifiers): references to release entities that this file represents a manifestation of. Note that a single file can contain multiple release references (eg, a PDF containing a full issue with many articles), and that a release will often have multiple files (differing only by watermarks, or different digitizations of the same printed work, or variant MIME/media types of the same published work).


Warning: This schema is not yet stable.

  • manifest (array of objects): each entry represents a file
    • path (string, required): relative path to file (including filename)
    • size (integer, required): in bytes
    • md5 (string): MD5 hash in lower-case hex
    • sha1 (string): SHA-1 hash in lower-case hex
    • sha256 (string): SHA-256 hash in lower-case hex
    • extra (object): any extra metadata about this specific file
  • urls: An array of "typed" URLs. Order is not meaningful, and may not be preserved.
    • url (string, required): Eg: "https://example.edu/~frau/prcding.pdf".
    • rel (string, required): Eg: "webarchive".
  • release_ids (array of string identifiers): references to release entities


Warning: This schema is not yet stable.

  • cdx (array of objects): each entry represents a distinct web resource (URL). First is considered the primary/entry. Roughly aligns with CDXJ schema.
    • surt (string, required): sortable URL format
    • timestamp (string, datetime, required): ISO format, UTC timezone, with Z prefix required, with second (or finer) precision. Eg, "2016-09-19T17:20:24Z". Wayback timestamps (like "20160919172024") should be converted naively.
    • url (string, required): full URL
    • mimetype (string): content type of the resource
    • status_code (integer, signed): HTTP status code
    • sha1 (string, required): SHA-1 hash in lower-case hex
    • sha256 (string): SHA-256 hash in lower-case hex
  • archive_urls: An array of "typed" URLs where this snapshot can be found. Can be wayback/memento instances, or direct links to a WARC file containing all the capture resources. Often will only be a single archive. Order is not meaningful, and may not be preserved.
    • url (string, required): Eg: "https://example.edu/~frau/prcding.pdf".
    • rel (string, required): Eg: "wayback" or "warc"
  • original_url (string): base URL of the resource. May reference a specific CDX entry, or maybe in normalized form.
  • timestamp (string, datetime): same format as CDX line timestamp (UTC, etc). Corresponds to the overall capture timestamp. Can be the earliest of CDX timestamps if that makes sense
  • release_ids (array of string identifiers): references to release entities


  • title (string, required): the display title of the release. May include subtitle.
  • original_title (string): the full original language title, if title is translated
  • work_id (fatcat identifier; required): the (single) work that this release is grouped under. If not specified in a creation (POST) action, the API will auto-generate a work.
  • container_id (fatcat identifier): a (single) container that this release is part of. When expanded the container field contains the full container entity.
  • release_type (string, controlled set): represents the medium or form-factor of this release; eg, "book" versus "journal article". Not necessarily the same across all releases of a work. See definitions below.
  • release_status (string, controlled set): represents the publishing/review lifecycle status of this particular release of the work. See definitions below.
  • release_date (string, ISO date format): when this release was first made publicly available. Blank if only year is known.
  • release_year (integer): year when this release was first made publicly available; should match release_date if both are known.
  • doi (string): full DOI number, lower-case. Example: "10.1234/abcde.789". See the "External Identifiers" section of style guide.
  • wikidata_qid (string): external identifier for Wikidata entities. These are integers prefixed with "Q", like "Q4321". Each release entity can be associated with at most one Wikidata entity (this field is not an array), and Wikidata entities should be associated with at most a single release. In the future it may be possible to associate Wikidata entities with work entities instead. See the "External Identifiers" section of style guide.
  • isbn13 (string): external identifier for books. ISBN-9 and other formats should be converted to canonical ISBN-13. See the "External Identifiers" section of style guide.
  • pmid (string): external identifier for PubMed database. These are bare integers, but stored in a string format. See the "External Identifiers" section of style guide.
  • pmcid (string): external identifier for PubMed Central database. These are integers prefixed with "PMC" (upper case), like "PMC4321". See the "External Identifiers" section of style guide.
  • core_id (string): external identifier for the [CORE] open access aggregator. These identifiers are integers, but stored in string format. See the "External Identifiers" section of style guide.
  • arxiv_id (string) external identifier to a (version-specific) arxiv.org work
  • jstor_id (string) external identifier for works in JSTOR
  • volume (string): optionally, stores the specific volume of a serial publication this release was published in. type: string
  • issue (string): optionally, stores the specific issue of a serial publication this release was published in.
  • pages (string): the pages (within a volume/issue of a publication) that this release can be looked up under. This is a free-form string, and could represent the first page, a range of pages, or even prefix pages (like "xii-xxx").
  • publisher (string): name of the publishing entity. This does not need to be populated if the associated container entity has the publisher field set, though it is acceptable to duplicate, as the publishing entity of a container may differ over time. Should be set for singleton releases, like books.
  • language (string, slug): the primary language used in this particular release of the work. Only a single language can be specified; additional languages can be stored in "extra" metadata (TODO: which field?). This field should be a valid RFC1766/ISO639 language code (two letters). AKA, a controlled vocabulary, not a free-form name of the language.
  • license_slug (string, slug): the license of this release. Usually a creative commons short code (eg, CC-BY), though a small number of other short names for publisher-specific licenses are included (TODO: list these).
  • contribs (array of objects): an array of authorship and other creator contributions to this release. Contribution fields include:
    • index (integer, optional): the (zero-indexed) order of this author. Authorship order has significance in many fields. Non-author contributions (illustration, translation, editorship) may or may not be ordered, depending on context, but index numbers should be unique per release (aka, there should not be "first author" and "first translator")
    • creator_id (identifier): if known, a reference to a specific creator
    • raw_name (string): the name of the contributor, as attributed in the text of this work. If the creator_id is linked, this may be different from the display_name; if a creator is not linked, this field is particularly important. Syntax and name order is not specified, but most often will be "display order", not index/alphabetical (in Western tradition, surname followed by given name).
    • role (string, of a set): the type of contribution, from a controlled vocabulary. TODO: vocabulary needs review.
    • extra (string): additional context can go here. For example, author affiliation, "this is the corresponding author", etc.
  • refs (array of ident strings): references (aka, citations) to other releases. References can only be linked to a specific target release (not a work), though it may be ambiguous which release of a work is being referenced if the citation is not specific enough. Reference fields include:
    • index (integer, optional): reference lists and bibliographies almost always have an implicit order. Zero-indexed. Note that this is distinct from the key field.
    • target_release_id (fatcat identifier): if known, and the release exists, a cross-reference to the Fatcat entity
    • extra (JSON, optional): additional citation format metadata can be stored here, particularly if the citation schema does not align. Common fields might be "volume", "authors", "issue", "publisher", "url", and external identifiers ("doi", "isbn13").
    • key (string): works often reference works with a short slug or index number, which can be captured here. For example, "[BROWN2017]". Keys generally supersede the index field, though both can/should be supplied.
    • year (integer): year of publication of the cited release.
    • container_title (string): if applicable, the name of the container of the release being cited, as written in the citation (usually an abbreviation).
    • title (string): the title of the work/release being cited, as written.
    • locator (string): a more specific reference into the work/release being cited, for example the page number(s). For web reference, store the URL in "extra", not here.
  • abstracts (array of objects): see below
    • sha1 (string, hex, required): reference to the abstract content (string). Example: "3f242a192acc258bdfdb151943419437f440c313"
    • content (string): The abstract raw content itself. Example: <jats:p>Some abstract thing goes here</jats:p>
    • mimetype (string): not formally required, but should effectively always get set. text/plain if the abstract doesn't have a structured format
    • lang (string, controlled set): the human language this abstract is in. See the lang field of release for format and vocabulary.

extra Fields

  • crossref (object), for extra crossref-specific metadata
    • subject (array of strings) for subject/category of content
    • type (string) raw/original Crossref type
    • alternative-id (array of strings)
    • archive (array of strings), indicating preservation services deposited
    • funder (object/dictionary)
  • aliases (array of strings) for additional titles this release might be known by
  • container_name (string) if not matched to a container entity
  • subtitle (string)
  • group-title (string) for releases within an collection/group
  • translation_of (release identifier) if this release is a translation of another (usually under the same work)
  • withdrawn_date (string, ISO date format): if this release has been retracted (post-publication) or withdrawn (pre- or post-publication), this is the datetime of that event. Retractions also result in a retraction release under the same work entity. This is intended to migrate from "extra" to a full release entity field.

release_type Vocabulary

This vocabulary is based on the CSL types, with a small number of (proposed) extensions:

  • article-magazine
  • article-journal, including pre-prints and working papers
  • book
  • chapter is allowed as they are frequently referenced and read independent of the entire book. The data model does not currently support linking a subset of a release to an entity representing the entire release. The release/work/file distinctions should not be used to group multiple chapters under a single work; a book chapter can be it's own work. A paper which is republished as a chapter (eg, in a collection, or "edited" book) can have both releases under one work. The criteria of whether to "split" a book and have release entities for each chapter is whether the chapter has been cited/reference as such.
  • dataset
  • entry, which can be used for generic web resources like question/answer site entries.
  • entry-encyclopedia
  • manuscript
  • paper-conference
  • patent
  • post-weblog for blog entries
  • report
  • review, for things like book reviews, not the "literature review" form of article-journal, nor peer reviews (see peer_review)
  • speech can be used for eg, slides and recorded conference presentations themselves, as distinct from paper-conference
  • thesis
  • webpage
  • peer_review (fatcat extension)
  • software (fatcat extension)
  • standard (fatcat extension), for technical standards like RFCs
  • abstract (fatcat extension), for releases that are only an abstract of a larger work. In particular, translations. Many are granted DOIs.
  • editorial (custom extension) for columns, "in this issue", and other content published along peer-reviewed content in journals. Many are granted DOIs.
  • letter for "letters to the editor", "authors respond", and sub-article-length published content. Many are granted DOIs.
  • stub (fatcat extension) for releases which have notable external identifiers, and thus are included "for completeness", but don't seem to represent a "full work".

An example of a stub might be a paper that gets an extra DOI by accident; the primary DOI should be a full release, and the accidental DOI can be a stub release under the same work. stub releases shouldn't be considered full releases when counting or aggregating (though if technically difficult this may not always be implemented). Other things that can be categorized as stubs (which seem to often end up mis-categorized as full articles in bibliographic databases):

  • commercial advertisements
  • "trap" or "honey pot" works, which are fakes included in databases to detect re-publishing without attribution
  • "This page is intentionally blank"
  • "About the author", "About the editors", "About the cover"
  • "Acknowledgments"
  • "Notices"

All other CSL types are also allowed, though they are mostly out of scope:

  • article (generic; should usually be some other type)
  • article-newspaper
  • bill
  • broadcast
  • entry-dictionary
  • figure
  • graphic
  • interview
  • legislation
  • legal_case
  • map
  • motion_picture
  • musical_score
  • pamphlet
  • personal_communication
  • post
  • review-book
  • song
  • treaty

For the purpose of statistics, the following release types are considered "papers":

  • article-journal
  • chapter
  • paper-conference
  • thesis

release_status Vocabulary

These roughly follow the DRIVER publication version guidelines, with the addition of a retracted status.

  • draft is an early version of a work which is not considered for peer review. Sometimes these are posted to websites or repositories for early comments and feedback.
  • submitted is the version that was submitted for publication. Also known as "pre-print", "pre-review", "under review". Note that this doesn't imply that the work was every actually submitted, reviewed, or accepted for publication, just that this is the version that "would be". Most versions in pre-print repositories are likely to have this status.
  • accepted is a version that has undergone peer review and accepted for published, but has not gone through any publisher copy editing or re-formatting. Also known as "post-print", "author's manuscript", "publisher's proof".
  • published is the version that the publisher distributes. May include minor (gramatical, typographical, broken link, aesthetic) corrections. Also known as "version of record", "final publication version", "archival copy".
  • updated: post-publication significant updates (considered a separate release in Fatcat). Also known as "correction" (in the context of either a published "correction notice", or the full new version)
  • retraction for post-publication retraction notices (should be a release under the same work as the published release)

Note that in the case of a retraction, the original publication does not get status retracted, only the retraction notice does. The original publication does get a widthdrawn_date metadata field set.

When blank, indicates status isn't known, and wasn't inferred at creation time. Can often be interpreted as published, but be careful!

contribs.role Vocabulary

  • author
  • translator
  • illustrator
  • editor

All other CSL role types are also allowed, though are mostly out of scope for Fatcat:

  • collection-editor
  • composer
  • container-author
  • director
  • editorial-director
  • editortranslator
  • interviewer
  • original-author
  • recipient
  • reviewed-author

If blank, indicates that type of contribution is not known; this can often be interpreted as authorship.


Works have no fields! They just group releases.