I'm not a scholar, nor do I play one on TV, but when I search Google Scholar I find that I'm cited there a few times, most notably for a 1994 BYTE cover story, Componentware. The details there are at best of historical interest but the topic remains evergreen: How do we package software in ways that maximize its reusability while minimizing the level of skill required to achieve reuse?
By 1996 the web had booted up and I reprised the theme in On-Line Componentware1. That's when it dawned on me that the websites that people "surfed" to were also software components that could be woven together to create novel effects. It was my first glimpse of what we later came to know as SOA (service-oriented architecture), then RESTful APIs, and most recently microservices. Ever since then, wearing one hat or another, I've been elaborating the theme of that column: "A powerful capability for ad hoc distributed computing arises naturally from the architecture of the Web." (link)
That architecture has in some ways remained the same, in other ways evolved dramatically, but its generative power continues to surprise and delight me. And I keep finding new ways to package and reuse web components.
Hypothesis has been a fascinating case study. Our web annotation system has two main components. The web service, written in Python, runs on a web server. The client, written in JavaScript, runs in your browser. Both are available for reuse in many different ways.
One way to reuse the web service is to embed views in web pages, as shown in this example from the Digipo project:
The "Matching Annotations" widget embedded in that page is just this search result wrapped in an iframe. This is one of the most common and powerful ways to reuse web components.
The Hypothesis API affords another way to reuse the web service. The Timeline widget, embedded on that same page, works that way. It searches Hypothesis for the URLs of annotations tagged with the id of the wiki page. Then it searches the annotations on each of those URLs for another user-assigned tag that signifies the publication date, and arranges those results chronologically. (The Timeline widget could have been written in PHP to run in the wiki server, but I'm more familiar with JavaScript so instead it's written in JS and runs in the browser.)
The Hypothesis client can also be reused in powerful ways. Most notably, you can add the client to a website by including this simple script tag in the site's main template:
<script async defer src="https://hypothes.is/embed.js"></script>
Or you can use the Hypothesis proxy, https://via.hypothes.is/, to inject the client into a web page, for example: https://via.hypothes.is/https://en.wikipedia.org/wiki/Proxy_server.
When you use Hypothesis to annotate a PDF file, it relies on a separate component -- Mozilla's PDF.js -- to parse the PDF and render it in the browser so the Hypothesis client can operate on it. PDF.js is available natively in Firefox, the Hypothesis Chrome extension injects it when you annotate a PDF in that browser.
Another Hypothesis component, pdf.js-hypothesis, which enables a web server to serve a PDF with PDF.js and Hypothesis both active. That makes PDF annotation available in any browser. We use it in our prototype Canvas app, for example, to serve annotation-enabled PDFs in the Canvas LMS.
Still another component enables custom rendering of annotations. You can see it in action at Science in the Classroom, a collection of research papers annotated to serve as teaching materials.
Graduate students use Hypothesis to create the annotations. But Science in the Classroom prefers to display them using its own mechanism, Learning Lens. So when the page loads, it fetches annotations using the Hypothesis API and then paints them on the page using a component that's part of the Hypothesis client but is also available as the standalone NPM module dom-anchor-text-quote.
I am deliberately blurring the definition of web component because I think it properly encompasses many different things: a web page embedded in an iframe; an API-accessible web service; a full-featured JavaScript application like Hypothesis -- or a simple JS widget like the Timeline -- embedded in a web page; a standalone module like dom-anchor-text-quote; a repackaging of Hypothesis as a WordPress plugin or a Canvas external tool.
This is a rich assortment of ingredients! But there's one that's notably absent. We've seen lots of ways to use the Hypothesis client as a component that plugs into other environments and makes annotation available there. But what if you want to plug something into the Hypothesis client? There isn't yet a mechanism for that. The code is open source and can be modified, as Marija Katic and Martin Eve have done with Annotran, a translation tool based on Hypothesis. That's a great example of code reuse. But it isn't, at least to my way of thinking, an example of component reuse. Although I recognize many different species of software components, they all share one piece of common DNA: reuse without internal modification.
As I've discussed elsewhere, though, that entails