Open Annotation / Web Annotation

Open Annotation Project


The Open Annotation Project started in 2009 and ended in 2013. Outcomes of this project helped to inform the work of the Open Annotation Community Group and the work of the W3C Web Annotation Working Group. In July 2016 the Working Group published 3 Candidate Recommendations:


Annotating is a pervasive element of scholarly practice for both the humanist and the scientist. It is a method by which scholars organize existing knowledge and facilitate the creation and sharing of new knowledge. It is used by individual scholars when reading as an aid to memory, to add commentary, and to classify.

It can facilitate shared editing, scholarly collaboration, and pedagogy. Over time annotations can have scholarly value in their own right. Yet scholars remain dissatisfied with the options available for annotating digital resources. Scholars wanting to annotate have to learn different annotation clients for different content repositories, have no easy way to integrate annotations made on different systems or created by colleagues using other tools, and are often limited to simplistic and constrained models of annotation.

The importance of annotating as a scholarly practice coupled with the real-world limitations of existing practices and tools supporting annotation of digital content has had a retarding effect on the growth of digital scholarship and the level of digital resource use by scholars.


The overarching goals of this project (consisting of multiple phases) are:

  • To facilitate the emergence of a Web and Resource-centric interoperable annotation environment that allows leveraging annotations across the boundaries of annotation clients, annotation servers, and content collections. To this end, interoperability specifications will be devised.

  • To demonstrate through implementations an interoperable annotation environment enabled by the interoperability specifications in settings characterized by a variety of annotation client/server environments, content collections, and scholarly use cases.

  • To seed widespread adoption by deploying robust, production-quality applications conformant with the interoperable annotation environment in ubiquitous and specialized services, tools, and content used by scholars – e.g.: Zotero, AXE, LORE, Co-Annotea, Pliny; JSTOR, AustLit, MONK.

About Open Annotation

Open Annotation Community Group


The purpose of the Open Annotation Community Group is to work towards a common, RDF-based, specification for annotating digital resources. The effort will start by working towards a reconciliation of two proposals that have emerged over the past two years: the Annotation Ontology [1] and the Open Annotation Model [2]. Initially, editors of these proposals will closely collaborate to devise a common draft specification that addresses requirements and use cases that were identified in the course of their respective efforts.


The goal is to make this draft available for public feedback and experimentation in the second quarter of 2012. The final deliverable of the Open Annotation Community Group will be a specification, published under an appropriate open license, that is informed by the existing proposals, the common draft specification, and the community feedback.

[1] Google Code Archive - Long-term storage for Google Code Project Hosting.
[2] Open Annotation: Beta Data Model Guide

W3C Web Annotation Working Group


The W3C Web Annotation Working Group is part of the Publishing@W3C, but the scope is more than just publishing; Web annotation is for all content on all devices.

A detailed list of this group’s publications is available in the working group’s specification repository.

The W3C Web Annotation Working Group is chartered to develop a set of specifications for an interoperable, sharable, distributed Web Annotation architecture.

Over the course of its charter, this group has created the following Recommendations:

The Working Group has also published a separate note on Embedding Web Annotations in HTML, exploring various ways annotations can be added to an HTML file using current specifications like JSON-LD or RDFa.

Finally, the selectors and states defined in the Web Annotation Data Model specification has also been extracted into a Working Group Note, which is intended to make the use of these classes easier and more broadly usable by other specifications.

The needs of a Client-Side API for Annotations as well as the topic of Robust Anchoring were under exploration, but not output were produced during the current charter.

What are Web Annotations?

Traditional annotations are marginalia, errata, and highlights in printed books, maps, picture, and other physical media. Web annotations are an attempt to recreate and extend that functionality as a new layer of interactivity and linking on top of the Web.

It will allow anyone to annotate anything anywhere, be it a web page, an ebook, a video, an image, an audio stream, or data in raw or visualized form. Web annotations can be linked, shared between services, tracked back to their origins, searched and discovered, and stored wherever the author wishes; the vision is for a decentralized and open annotation infrastructure.

For a detailed high-level overview of this idea, see the proposed Web annotation architecture diagram.

What’s the relationship with Open Annotations?

The Open Annotation Community Group is an informal public group that created an RDF-based data model for exchanging annotations between applications. This data model was described in the Open Annotation Data Model specification. The Web Annotation WG has a broader scope, including the development of server-side and client-side APIs and other missing pieces of the annotation architecture. We will use the Open Annotation specs as the basis for a more formal data model standard.

The OA CG will still continue driving use cases and requirements, and further discussion of annotation issues that are outside the scope of the Web Annotation WG. It’s expected that there will be an ongoing relationship between the two groups, and an overlap of participants.

Architecture diagram