URId

URId, an acronym for Uniform Resource Identifier, is a string of characters used to identify a resource. A resource can be anything, such as a physical object, a concept, or a digital document. URIs are fundamental to the functioning of the World Wide Web and many other internet protocols. They provide a consistent way to refer to information regardless of its location or format.

URIs are composed of several components, including a scheme, a hierarchical part, and optionally a query and fragment. The scheme, such as "http" or "ftp," indicates the protocol used to access the resource. The hierarchical part typically includes a domain name or IP address, and a path to the specific resource. The query provides additional parameters, while the fragment points to a specific section within a resource.

Two common and important subsets of URIs are Uniform Resource Locators (URLs) and Uniform Resource Names (URNs). URLs specify the location of a resource and how to access it, essentially acting as an address. URNs, on the other hand, aim to provide a persistent and unique identifier for a resource, independent of its location. While all URLs and URNs are URIs, not all URIs are necessarily URLs or URNs. The widespread adoption of URIs has been crucial for the organization and retrieval of information in the digital age.