URI, URL and urn difference, relation and syntax diagram

Definition

• URI = Universal Resource Identifier Uniform resource identifier
• URL = Universal Resource Locator Uniform resource locator
• URN = Universal Resource Name Unified resource name

Relationship

The relationship among the three is shown in the figure below ：

URI There are three kinds of ：

• URL : Represents the path address of the resource , It doesn't have to be HTTP URL （http://）,URL It can also be （ftp://） or （smb://）
• URN ： Represents the unique name of the resource , It does not mean that the identified resources are available .
• URL & URI ： It also contains the path address and unique name of the resource

give an example

RFC3986 Example :

URL: ftp://ftp.is.co.za/rfc/rfc1808.txt
URL: http://www.ietf.org/rfc/rfc2396.txt
URL: ldap://[2001:db8::7]/c=GB?objectClass?one
URL: mailto:John.[email protected].com
URL: news:comp.infosystems.www.servers.unix
URL: telnet://192.0.2.16:80/
URN (not URL): urn:oasis:names:specification:docbook:dtd:xml:4.1.2
URN (not URL): tel:[phone] (?)

grammar

Wikipedia

URL Grammar diagram , as follows

URI Grammar diagram , as follows ：