Making it easier to share annotations on the Web

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The W3C has announced the publication of three new standards aimed to enable an ecosystem of interoperable products that let the world comment on, describe, tag, and link any resource on the Web. Many websites already allow comments, but current annotation systems rely on unique, usually proprietary technologies chosen and provided by publishers. Notes cannot be shared easily across the Web and comments about a Web page can only be saved and viewed via a single website. Readers cannot select their own tools, choose their own service providers or bring their own communities. The adoption of the Web Annotation standards will spell the end of the phrase "Don't read the comments!", returning power to the readers decide where and how they provide and consume such feedback.

What the Web Annotation standards do

The three new standards describe how to precisely identify the target, body and metadata of an annotation of a Web resource. They provide a basic data structure and protocol to ensure interoperability among annotation systems, but they do not dictate how annotation tools and services are realized in terms of user interface features and functionality. Each of the standards serves a specific purpose:

  • The Annotation Data Model provides the structure and details for any web developer to quickly build out compatible tools and content. It gives use cases and examples for the JSON structures to create and consume.
  • The Annotation Vocabulary projects the data model into Linked Data, providing a solid and future-proof foundation to enable extension and semantic understanding. In fact, the JSON structures of the Data Model are already semantic as well as easy to implement, via the magic of the JSON-LD specification.
  • The Annotation Protocol provides a simple RESTful HTTP API for communicating among annotation clients and servers, and builds upon the Linked Data Platform specification.

These specifications provide the foundational material for a new generation of annotation tools on the Web while still leaving developers free to address specific use cases with tailored interfaces and services. This will encourage new innovations and the emergence of community-based best practices. For example, The W3C Working Group Note on Embedding Web Annotations in HTML, published concurrently with the three Web Annotation Recommendations, describes and illustrates just a few of the potential approaches for including annotations within HTML documents, serving as a starting point for further discussion, experimentation and development.

Getting This Far and What's Ahead

The work on the annotation specifications started in 2009 with two independent groups, the Annotation Ontology and the Open Annotation Collaboration (both of which built upon the early W3C project: Annotea). In 2011, the two groups joined forces to help found the W3C Open Annotation Community Group. In 2013 this Community Group published a series of initial draft specifications. 2014 saw the creation of the Web Annotation Working Group to take the work through the standardization process and further the engagement with the web community, resulting in the specifications published on February 23rd, 2017.

As a diverse group of Web developers, publishers, and content creators note below, this work is and will be increasingly important as the volume and speed of information publishing continue to grow. The world has seen a dramatic increase in the spread of misinformation and "fake news", and the web previously lacked a decentralized, trustworthy mechanism for fact checking and public discussion. Cory Doctorow, of the Electronic Frontier Foundation and the award-winning, describes the importance of annotation in this space:

We are absolutely delighted to see these recommendations land and endorse them in full. Though much hard work remains to be done, a formal standard for a universal web annotation layer is a critical step in the development of this promising new paradigm.

The broad, growing interest in Web annotation tools and services magnifies the likely impact of these specifications. As Dan Whaley, of and the Annotating All Knowledge coalition, notes, the publication of these Recommendations means that:

Annotation has now become a formal part of the Web —-- the importance of which cannot be overstated. Over seventy major publishers and platforms under the Annotating All Knowledge coalition have pledged to include interoperable annotations as a collaborative framework over their content, and these implementations can now move forward with confidence. More importantly, browsers can now consider enabling users to listen for conversations on every page on the Web as a native capability.

Another domain that directly benefits from these standards is the multi-billion-dollar e-book publishing sector. Sharing annotations from your ePub reader — whether on your phone, computer, or dedicated device — and interacting with others regardless of their particular platform, enables massive and rapid improvements in teaching and learning at all levels. Patrick Johnston, Director of Platform Architecture, Product Technology, at the publisher John Wiley & Sons, Inc. describes the importance of the work:

We've used the Open Annotation Community Group’s Data Model at Wiley for some time. The Web Annotation specifications provide some needed improvements and additional guidance we're working to implement and look forward to continued collaboration around annotation in digital publishing.

The traditions of scholarly discourse in sharing comments, annotations, etc., is a significant use case which can now be brought into the digital age of scholarly publishing. The same is true in areas like digital cultural heritage. Sheila Rabun is the Community and Communications Officer for the IIIF Consortium (International Image Interoperability Framework), currently consisting of 40 primarily academic and cultural heritage organizations including the national libraries of Britain, France, Israel, Norway, and Poland, and universities such as Stanford, Harvard, Cornell, Yale, Princeton, MIT, Oxford, Cambridge, and Tokyo. She describes the standards' importance in that community:

The work done in IIIF could not happen without the groundbreaking specifications coming from the Open Annotation and Web Annotation groups. Annotation is a fundamental part of the IIIF model, and our most asked-for and discussed feature in implementations. It increases the visibility of digital cultural heritage and enables distributed online scholarship.

Acknowledgments and Further Information

We would like to thank everyone that has been involved throughout the process. In particular the previous co-chair, Frederick Hirsch; the W3C staff contacts, Ivan Herman and Doug Schepers; the other editors of the specifications, Benjamin Young and Paolo Ciccarese; the members of the Web Annotation Working Group, and the members of the Open Annotation Community Group. We are grateful for the past, present, and future work underway around these specifications.

For further information please contact the Chairs of the Web Annotation Working Group, Dr. Robert Sanderson (J. Paul Getty Trust, and Prof. Timothy Cole (University of Illinois at Urbana-Champaign, To comment on or discuss potential uses of the Web Annotation Recommendations, or to post news and updates about your implementations of these specifications, please join the W3C Open Annotation Community Group.

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