Citations as First-Class Data Entities: Introduction

Citations are now centre stage

As a result of the Initiative for Open Citations (I4OC), launched on April 6 last year, almost all the major scholarly publishers now open the reference lists they submit to Crossref, resulting in more than half a billion references being openly available via the Crossref API.

It is therefore time to think carefully about how citations are treated, and how they might be better handled as part of the Linked Open Data Web.

Citations are normally treated simply as the links between published entities.

However, an alternative richer view is to regard a citation as a data entity in its own right.

This permits us to endow a citation with descriptive properties, such as

has citation creation date:   3rd March 2015
has citation time span:       6 years, 5 months and 23 days
has type:                     Self-citation
has identifier:               oci:7295288-3962641

[Note: a later blog post entitled “Open Citation Identifiers” will include an explanation of the identifier shown here.]

Advantages of treating citations as First-Class Data Entities

• All the information regarding each citation is available in one place.
• Citations become easier to describe, distinguish, count and process.
• If available in aggregate, citations described in this manner are easier to analyze using bibliometric methods, for example to determine how citation time spans vary by discipline.

Requirements for citations to be treated as First-Class Data Entities

• They must be definable in a machine-readable manner as a member of the class “Citation”, and describable using appropriate ontology terms.
• They must have metadata structured using a generic yet appropriately detailed data model.
• They must be storable, searchable and retrievable in an open database designed for bibliographic citations.
• They must be identifiable using a global persistent identifier scheme.
• There must be a Web-based identifier resolution service that takes the citation identifier as input and returns a description of the citation.

Blog post detailing how these requirements are met

Subsequent blog posts will describe how we at OpenCitations have satisfied these requirements, permitting citations to indeed be treated as First-Class Data Entities:

1. Citations as First-Class Data Entities: Citation Descriptions
2. Citations as First-Class Data Entities: The OpenCitations Data Model
3. Citations as First-Class Data Entities: The OpenCitations Corpus
4. Citations as First-Class Data Entities: Open Citation Identifiers
5. Citations as First-Class Data Entities: The Open Citation Identifier Resolution Service