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URI, URL, URN

URI, URL, URN

This post analyzes URI, URL, and URN.

1. URI (Uniform Resource Identifier)

[Figure 1] URI, URL, URN Relationship

[Figure 1] URI, URL, URN Relationship

URI means, as the name implies, a unique identifier attached to a Resource. Here, a Resource mainly refers to a Web Resource used on the internet. A URI consists of a URL, which is used to indicate the location of a Web Resource, and a URN, which indicates the name of a Web Resource. [Figure 1] shows the relationship between URI, URL, and URN.

2. URL (Uniform Resource Locator)

[Figure 2] URL

[Figure 2] URL

A URL is used, as the name implies, to give unique location information to a Web Resource. [Figure 2] shows an example of a URL. The components of a URL are as follows. For the term Root Domain, the common meaning and the meaning from the DNS perspective are different. [Figure 2] shows both meanings to avoid confusion.

  • Scheme : Generally refers to the Protocol for accessing the Web Resource.
  • Root Domain (DNS View) : From the DNS perspective, the Root Domain refers to the topmost Domain. It is represented by . and is generally omitted.
  • Top-level Domain : Refers to the top-level Domain. There are ccTLDs (country code TLD) such as .kr and .us, and gTLDs (generic TLD) such as .com and .net.
  • Domain Name / Second-level Domain : Refers to the Domain name, and since it is a sub-Domain of the Top-Level Domain, it is also called the Second-level Domain.
  • Root Domain (Common) : The common Root Domain refers to the combination of the Domain Name and the Top-level Domain.
  • Subdomain / Third-level Domain : Refers to an auxiliary Domain, and since it is a sub-Domain of the Second-level Domain, it is also called the Third-level Domain. It is also possible to compose a Domain with multiple Depths by configuring multiple Subdomains.
  • FQDN : Refers to the combination of all Domains.
  • Port : Refers to the Port for accessing the Web Resource, and it can be omitted when using the Default Port used for each Scheme. Ex) HTTP/80, HTTPS/443
  • Subdirectory : Refers to the Path under the Domain. Depth can be expressed using the / character.
  • Query String : Used to pass Parameters to a Web Resource through the URL. It starts at the end of the URL with the ? character and has the form <key>=<value>. Multiple Key-Values can be set using multiple & characters.

3. URN (Uniform Resource Name)

[Figure 3] URN

[Figure 3] URN

A URN is used, as the name implies, to give a unique name to a Web Resource. [Figure 3] shows an example of a URN. The components of a URN are as follows.

  • NID (Namespace Identifier) : Represents the Namespace.
  • NSS (Namespace Specific String) : Refers to a unique String value within the Namespace. To express Depth like the Subdirectory of a URL, a URN sometimes expresses Depth through the : character, and even in this case, all parts except the NID part are regarded as the NSS.
urn:isbn:0451450523a (Book Number)
urn:isan:0000-0000-2CEA-0000-1-0000-0000-Y (Move Number)
urn:uuid:6e8bc430-9c3a-11d9-9669-0800200c9a66 (UUID)
urn:mpeg:mpeg7:schema:2001<br/>
[Text 1] URN Example

[Text 1] shows examples of URNs.

4. References

Union Mount, AUFS, Docker Image LayerUUID