URI
A Uniform Resource Identifier (URI) is a unique sequence of characters that identifies a logical or physical resource used by web technologies. URIs may be used to identify anything, including real-world objects, such as people and places, concepts, or information resources such as web pages and books.
Some URIs provide a means of locating and retrieving information resources on a network; these are Uniform Resource Locators (URLs). A URL provides the location of the resource. A URI identifies the resource by name at the specified location or URL.
Other URIs provide only a unique name, without a means of locating or retrieving the resource or information about it, these are Uniform Resource Names (URNs).
URIs are not only used by Browsers. They are also used to identify anything in RDF and OWL.
The URI syntax is:
textSome examples:
userinfo host port
┌──┴───┐ ┌──────┴──────┐ ┌┴┐
https://john.doe@www.example.com:123/forum/questions/?tag=networking&order=newest#top
└─┬─┘ └───────────┬──────────────┘└───────┬───────┘ └───────────┬─────────────┘ └┬┘
scheme authority path query fragment
ldap://[2001:db8::7]/c=GB?objectClass?one
└┬─┘ └─────┬─────┘└─┬─┘ └──────┬──────┘
scheme authority path query
mailto:John.Doe@example.com
└─┬──┘ └────┬─────────────┘
scheme path
news:comp.infosystems.www.servers.unix
└┬─┘ └─────────────┬─────────────────┘
scheme path
tel:+1-816-555-1212
└┬┘ └──────┬──────┘
scheme path
telnet://192.0.2.16:80/
└─┬──┘ └─────┬─────┘│
scheme authority path
urn:oasis:names:specification:docbook:dtd:xml:4.1.2
└┬┘ └──────────────────────┬──────────────────────┘
scheme path
[[URI|URIs]] can only use a subset of characters. All other characters must be URL Encoded. IRI extends URIs by also allowing international characters.