Where is the difference between locating and identifying a resource? [duplicate]

This question already has answers here: Closed 12 years ago.

Possible Duplicate:

What's the difference between a URI and a开发者_JAVA百科 URL?

Is there any difference? I'm talking about URI for identifying, but URL for locating. Aren't both the same thing?

---

They can look the same, but they're not the same thing. A URL identifies something that can be transferred over some protocol (often http). A URI, can be used to identify a namespace (for example) but there might not be any content at the address.

---

Where is the difference between locating a ressource and identifying a ressource?

Knowing who I am doesn't tell you anything about where I am.

---

A URI identifies a resource either by location, or a name, or both. More often than not, most of us use URIs that defines a location to a resource.

A URL is a specialization of URI that defines the network location of a specific resource.

Generally, if the URL describes both the location and name of a resource, the term to use is URI.

---

This article might help:
URI vs. URL

Excerpt:

"...a URL is a type of URI that identifies a resource via a representation of its primary access mechanism (e.g., its network "location"), rather than by some other attributes it may have. Thus as we noted, "http:" is a URI scheme. An http URI is a URL. The phrase "URL scheme" is now used infrequently, usually to refer to some subclass of URI schemes..."

---

An identifier is a unique name for something, so we can be sure that we talk about the same thing. For example the Atom namespace is 'http://www.w3.org/2005/Atom'. This is a URI. This doesnt mean that you can put this URI in a browser and have a document there (well, in case of Atom, yes, you have a document, but it's a simple presentation of Atom for convenience, it's not the Atom namespace itself).

A URL is the location of a document. This is what you can put in your browser. It is confusing that both use the same format (http://...) but that is mostly annecdotic ...

---

A URL is a URI which is not a URN. (see)