From SMW+ Semantic Enterprise Wiki

Overview

URI’s (”Uniform Resource Identifiers”) are necessary for uniquely identifying and linking to resources on the web. A URI is basically a string that identifies a thing or resource on the web. All “Information Resources”, or WWW pages, documents, etc. have a URI, which is commonly known as a URL (Uniform Resource Locator).

Structure

The first part of an URI (before colon) specifies the type:

Schema:schema-specific part

Many URI-schemata like http or ftp have a hierarchical structure:

Schema://[User[:Password]@]Server[:Port][/Path][?Request][#Fragment-Identifier]

Server: specifies name of domain or ip-address of server, for schemata using TCP or UDP protocol
Port: specifies TCP port (optional and only if it deviates from standard port)
User and password: optional, useful for authentication of services
The last element of the URI can be a fragment-identifier, separated with a #. An example is the anchor in HTML.

The most significant schema is hypertext transfer protocol (HTTP). Hierarchical URIs can be specified relative to a one URI, which is the basis. In this case, schema, server and port can be left.

Glossary Term: URI

Uniform Resource Identifiers are necessary for uniquely identifying and linking to resources on the web.