How web annotation will transform content management

In February the W3C approved recommendations to enable annotation on the web. There is a long lineage of annotation tools that enable readers of the web to write comments that overlay content and attach to selections within it. Users of such tools will be happy to know that annotations can now be represented, stored, and exchanged by interoperable clients and servers. But the broader significance of this new standard is that, by defining how applications refer to selections within content, it increases the granularity of the web’s address space in ways that benefit many existing applications and will enable new ones.

In text, annotations attach to selected paragraphs, sentences, phrases, or numbers in cells of tables. In images they attach to selected regions, and in audio and video to selected clips. The W3C calls these selections segments of interest and defines how to find them within content. We find conventional web resources by way of Uniform Resource Locators (URLs). Such resources contain many possible segments. The act of annotation forms an address that locates a selectable segment within a resource, turning it into a new kind of web resource.

“The World Wide Web has succeeded,” wrote Roy Fielding in his famous dissertion, “in large part because its software architecture has been designed to meet the needs of an Internet-scale distributed hypermedia system.” In the early 2000s, as InfoWorld tracked the then-hot topic of web services, the web’s native architectural style, which Fielding called Representational State Transfer (REST), was just coming into focus.

Nowadays we more fully appreciate the power of a web of hyperlinked resources accessible at well-known global addresses and manipulated by a few basic commands like GET, POST, and DELETE. Annotation extends that power to a web made not only of linked resources, but also of linked segments within them. If the web is a loom on which applications are woven, then annotation increases the thread count of the fabric. Annotation-powered applications exploit the denser weave by defining segments and attaching data or behavior to them.

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