scope:

CP/LD draws on the strength of two widely used standard formats, HTML and JSON-LD, and can be applied to all digital content and files. However, as part of the standard's first release, its implementation focuses on text-based scholarly articles. Article data linkages, as described in the NISO work item proposal Integrating Publisher and Repository Workflows to Improve Research Data-Article Links,¹ are envisioned to link articles and research output but are outside the scope of this initial phase. The lessons from this phase can be adapted to other types of digital content and files.

This standard comprises two parts. These are documented in the following clauses:

1. Linked Documents: a set of rules that outline the minimal characteristics of documents that conform to this standard. Such documents are called Linked Documents.

2. Content Profiles: a mechanism, building on the W3C Publication Manifest profile recommendation,² to define more detailed requirements above and beyond the ones defined by this standard, for specific types of content and use cases.

Purpose

The demand for academic, research, and professional content has never been greater. However, technology has significantly changed the way in which this content is consumed. Users expect contextualized, bite-sized, targeted content delivered as a seamless part of their information processing. Content creators produce machine-actionable content, data, and other resources, and they desire to link this work to the work of others, both known and unknown, for discovery and dissemination. However, current document-based markup models are not designed to work this way.

The purpose of the Content Profile/Linked Document (CP/LD) standard is to define a flexible, extensible, standards-based format for combining content, data, and semantics intended as a machine-readable, self-describing markup that can be used to exchange data and content between systems, APIs, and services. By building on the HTML and JSON-LD standards, it allows linking in a much more distributed manner compared to other formats, whether between arbitrarily small chunks or large aggregations of content, while still providing enough structure to exchange content and data across processes, services, and workflows.

CP/LD does not have to replace existing models used for journal articles, books, data sets, or semantic and metadata schemes. Instead, these can be transformed as needed to CP/LD, enabling the combination of arbitrary portions of content, data, semantics, and other resources from separate sources into a single, standards-based format optimized for interchange, search, and display. Existing scholarly XML, such as JATS, can be used to create CP/LD documents, and vice versa, provided that the necessary information is present in the CP/LD document.

CP/LD content is stratified between structure and narrative and data semantics, with a well-defined pattern connecting them. Stratification enables addressing the specific requirements for each role. For instance, content and structure have an order, whereas narrative semantics and data semantics do not.

Extensibility is achieved through patterns and principles that allow the semantics and narrative structure to be enhanced for different use cases without impacting the base scheme.

Combining HTML and JSON-LD, two formats with different syntaxes, is not trivial, even when both are governed by the same underlying web standards from IETF and W3C. The CP/LD standard sets out the requirements for combining the two formats to remain consistent. All key identifying information about a document and its parts can be represented in both formats in an interconnected and interchangeable fashion.

Content Profiles allow for the specification of suitable expression of particular instances or types of all manner of content, and for meaningful exchange of that content across systems, based on the CP/LD specification. New Content Profiles can be developed in accordance with this standard. It is recommended to use widely adopted ontologies and schemas and to reuse and extend existing profiles where possible.