Annotation-powered apps: A “Hello World” example

Workflows that can benefit from annotation exist in many domains of knowledge work. You might be a teacher who focuses a class discussion on a line in a poem. You might be a scientist who marks up research papers in order to reason about connections among them. You might be an investigative journalist fact-checking a claim. A general-purpose annotation tool like Hypothesis, already useful in these and other cases, can be made more useful when tailored to a specific workflow.

I’ve tried a few different approaches to that sort of customization. For the original incarnation of the Digital Polarization Project, I made a Chrome extension that streamlined the work of student fact-checkers. For example, it assigned tags to annotations in a controlled way, so that it was easy to gather all the annotations related to an investigation.

To achieve that effect the Digipo extension repurposed the same core machinery that the Hypothesis client uses to convert a selection in a web page into the text quote and text position selectors that annotations use to identify and anchor to selections in web pages. Because the Digipo extension and the Hypothesis extension shared this common machinery, annotations created by the former were fully interoperable with those created by the latter. The Hypothesis client didn’t see Digipo annotations as foreign in any way. You could create an annotation using the Digipo tool, with workflow-defined tags, and then open that annotation in Hypothesis and add a threaded discussion to it.

As mentioned in Annotations are an easy way to Show Your Work, I’ve been unbundling the ingredients of the Digipo tool to make them available for reuse. Today’s project aims to be the “Hello World” of custom annotation-powered apps. It’s a simple working example of a powerful three-step pattern:

  1. Given a selection in a page, form the selectors needed to post an annotation that targets the selection.
  2. Lead a user through an interaction that influences the content of that annotation.
  3. Post the annotation.

For the example scenario, the user is a researcher tasked with evaluating the emotional content of selected passages in texts. The researcher is required to label the selection as StrongPositive, WeakPositive, Neutral, WeakNegative, or StrongNegative, and to provide freeform comments on the tone of the selection and the rationale for the chosen label.

Here’s the demo in action:

The code behind the demo is here. It leverages two components. The first encapsulates the core machinery used to identify the selection. The second provides a set of functions that make it easy to create annotations and post them to Hypothesis. Some of these provide user interface elements, notably the dropdown list of Hypothesis groups that you can also see in other Hypothesis-oriented tools like facet and zotero. Others wrap the parts of the Hypothesis API used to search for, or create, annotations.

My goal is to show that you needn’t be a hotshot web developer to create a custom annotation-powered app. If the pattern embodied by this demo app is of interest to you, and if you’re at all familiar with basic web programming, you should be able to cook up your own implementations of the pattern pretty easily.

To work with selections in web pages, annotation-powered apps like these have to get themselves injected into web pages. There are three ways that can happen, and the Hypothesis client exploits all of them. Browser extensions are the most effective method. The Hypothesis extension is currently available only for Chrome, but there’s a Firefox extension waiting in the wings, made possible by an emerging consensus around the WebExtensions model.

A second approach entails sending a web page through a proxy that injects an annotation-powered app into the page. The Hypothesis proxy,, does that.

Finally there’s the venerable bookmarklet, a snippet of JavaScript that runs in the context of the page when the user clicks a button on the browser’s bookmarks bar. Recent evolution of the browser’s security model has complicated the use of bookmarklets. The simplest ones still work everywhere, but bookmarklets that load helper scripts — like the HelloWorldAnnotated demo — are thwarted by sites that enforce Content Security Policy.

It’s a complicated landscape full of vexing tradeoffs. Here’s how I recommend navigating it. The HelloWorldAnnotated demo uses the bookmarklet approach. If you’re an instructional designer targeting Project Gutenberg, or a scientific developer targeting the scientific literature, or a newsroom toolbuilder targeting most sources of public information, you can probably get away with deploying annotation-powered apps using bookmarklets. It’s the easiest way to build and deploy such apps. If the sites you need to target do enforce Content Security Policy, however, then you’ll need to deliver the same apps by way of a browser extension or a proxy. Of those two choices, I’d recommend a browser extension, and if there’s interest, I’ll do a follow-on post showing how to recreate the HelloWorldAnnotated demo in that form.

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