The following blog post by Phil Windley of Kynetx describes the concept of declarative references to data:
http://www.windley.com/archives/2010/08/beyond_apis_declarative_references_to_data.shtml
Basically, the idea is that with XRI and XDI, it is possible to reference any part of a global graph of data, in a location independent way and at any arbitrary depth.
A simple example would be:
=markus/+email$
This is a GLOBAL reference to Markus’ e-mail address. An alternative reference to the same data (using a persistent I-Number) would be:
=!91F2.8153.F600.AE24/+email$
Provided that the necessary XDI Link Contracts are in place, it is possible to resolve =markus to an XDI endpoint, and then – using XDI messaging – retrieve the +email$ attribute, which points to a specific point in my XDI graph.
The above example points to the following piece of XDI data (in XDI/JSON format):
{
"=!91F2.8153.F600.AE24": {
"+email$": "markus.sabadello@gmail.com"
}
}
For more information on how to actually do this, see the following questions in our FAQ: