Like URLs, USGIN URIs can be entered into a web browser. Entering a USGIN URI into a web browser produces a representation of the resource identified by the URI. A representation is a symbolic proxy for something.

For example, a fault in the middle of the Mojave Desert can be represented by a symbol on a map, a digital photograph, or a text description of the fault.  A USGIN URI identifying this fault would typically dereference to an XML representation of the fault (Figure 1). This XML document would provide structured information about the fault's attributes, including the fault's age, dip, and slip. These attributes can be used for analysis.

Figure 1: The relationship between USGIN URIs, XML documents, and the resource identified by the USGIN URI

However: even though they dereference to a web page when entered into a web browser, USGIN URIs are not URLs.

URLs identify a location at which a bound resource may be found.  When entered into a web browser, a URL instructs the web browser to go to the indicated location and retrieve whatever resource is there.

By contrast: USGIN URIs are not URLs because the resource they identify is neither the representation found at the web location to which the USGIN URI dereferences, nor the web location at which said representation may be found

Returning to the example of a fault in the middle of the Mojave Desert: the fault is the resource identified by the USGIN URI.  The USGIN URI does not identify the representation of said fault, nor the location at which said representation may be found.  The USGIN URI identifies only the fault; the representation of the fault can be considered an intentional incidental.

Continue the tutorial by clicking the links below.