Physical Hyperlinks and Web/ID
The term internet of things, coined many years ago, is now prominent; meaning the system in which arbitrary physical entities with IP addresses interact directly, and in which their data is aggregated and processed by applications. Many, like us, prefer to formulate these interactions in terms of web protocols (HTTP etc), and term this the web of things. In the Cooltown project, which was seminal in this respect, we termed this the Real World Wide Web: the systematic linkage from physical entities to web resources. We should have used Physical World Wide Web, but that didn't sound as good! A related term we used was physical hyperlink. Sometimes physical hyperlinks take the form of URLs physically bound to the physical entities — for example, in the form of a Cooltown beacon that broadcasts the entity's URL to handheld devices nearby. But other times entities bear identifiers rather than URLs, in the form of barcodes or RFID, for example. web/id is the system that resolves identifiers such as tag URIs printed on or attached to physical entities, in order to link them to web resources.
- This interview provides a non-technical introduction to example applications that web/id is intended to enable.
- Implementing physical hyperlinks using ubiquitous identifier resolution (also available as an HP Technical Report in PDF format) given at the 11th International World Wide Web Conference. (This is an update on Ubiquitous and contextual identifier resolution for the real-world wide web, with mainly expositional changes.) HP Labs Tech. report HPL-2001-95R1.
- Tag URIs (RFC 4151, Tim Kindberg and Sandro Hawke) — a new type of URI that enables anyone who currently holds an email address or a domain name to construct a resource identifier that is unique for all time. This page has a unique tag URI at the end and in the title. You can find this page via a search engine from its tag. It turns out Leslie Lamport had a similar idea - see his "Archival References to Web Pages".
Viually distinctive barcodes
I experimented with 'organic' barcode designs, whose distinctive form indicated they linked to web content.
Note that all these barcodes can be conveniently read using a standard laser scanner. (In some cases, such as the wavy barcode, the user needs to see where the 'scan lines' are.)
If you use tag URIs as your identifiers, you have all the id technology you need to identify your electronic and non-electronic stuff.