I was completely new to the XRI (Extensible Resource Identifier) syntax, but then I came across this post from Drummond Reed’s weblog on “open tagging”.

XRI might be a solution for an open, distributed way of tagging content that does not rely on a single centralized “dictionary” provider (e.g., Technorati, PubSub, etc.) […]

So what’s the XRI solution? Switch from an HTTP URI to an identifier syntax specifically developed for abstract identifiers (including generic concepts like “Thai” that don’t exist as definitive HTTP URI resources). For example, the XRI-based open tag would look like this:

<a href="xri://+thai" rel="tag">Thai</a>

What’s the “+” stand for? It’s the XRI global context symbol for generic identifiers - identifiers that represent generic subjects, topics, or concepts for which there is no central authority, any more than there is any one authoritative dictionary for the meaning of the word “Thai” in the English language.

Bingo! That’s exactly what I was looking for: an abstract and global identifier to represent tags with features nicely suited to exploit the power of tagging.

Better still, XRI syntax allows an author to declare a explicit dictionary authority for a +word if they choose to. For example…

<a href="xri://technorati.com/(+thai)" rel="tag">Thai</a>

…would tell interpreters of this tag that the author is referring to the generic concept of “Thai” in the specific context of the dictionary provided by the authority “technorati.com”. The author can cite any authority they want, including themselves. For example, the following two examples would be two different ways of citing myself as the dictionary authority (the first using a DNS domain name address and the second an XRI i-name address):

<a href="xri://equalsdrummond.name/(+thai)" rel="tag">Thai</a>
<a href="xri://=drummond/(+thai)" rel="tag">Thai</a>

The theoretical foundations of XRI seem pretty robust and, quite oddly being the outcome of a technical committee, XRI is easy to understand and hopefully to implement.

I’ve the strange feeling that XRI will become a very important part of the clipperz projects …
More soon.