Uniform Resource Locator | Part 2

Uniform Resource Locator | Part 2

URI References

The term URI reference refers to a particular case of a URI, or a portion thereof, as used in an HTML document, for example, to refer to a particular resource. A URI reference usually looks like a URL or the end of a URL. URI references introduce two new concepts: the distinction between absolute and relative references, and the concept of a fragment identifier.

An absolute URL is a URI reference that is similar to the above-defined URL that starts with an outline (“:”) followed by a colon and a scheme-specific part. A relative URL is a URI reference that includes only the specific part of a URL scheme, or any component part of that monitoring. The layout and main components are inferred from the context in which it appears the reference URL: the base URI (or URL base) of the document containing the reference.

A URI reference may also be followed by a numeral character (“#”) and a pointer within the resource referenced by the URI as a whole. This is not part of the URI as such but is thought to be the “user agent (browser) will interpret after a representation of the resource has been recovered. It is therefore not meant to be sent to the server as HTTP requests.

Differentiation between upper / lowercase letters

According to the current standard in the scheme and host components are not case sensitive, and when normalized during processing, must be lowercase. Assume that it is in other components differentiation. However, in practice, other components besides the protocol and host, this differentiation is dependent on the web server and operating system that hosts the server system.

URL in everyday use

An HTTP URL combines in a single address the four basic elements of information needed to retrieve a resource from anywhere on the Internet:

•    The protocol used to communicate,
•    The host (server) with which it communicates,
•    The network port to connect to the server,
•    The path to the resource on the server (for example, your file name).

Many web browsers do not require the user to enter “http://” to target a web page, since HTTP is the most common protocol used in web browsers. Likewise, since 80 is the default port for HTTP, usually not specified. Usually you only enter a partial URL such as www.wikipedia.org / wiki / Train. To go to a homepage will enter only the hostname, as www.wikipedia.org.

Since the HTTP protocol allows a server to respond to a request by redirecting the web browser to a different URL, many additional servers allow users to skip certain parts of the URL, such as the “www.” numeral or character (” # “) to track whether the resource is a directory. However, these omissions are technically a different URL, so the browser can not make these adjustments, and must trust the server responds with a redirect. It is possible for a web server (but due to a strange tradition) offer two different pages for URLs that differ only in a “#” character.

Note that in es.wikipedia.org / wiki / Train, the hierarchy of the five elements is org (generic top level domain) – wikipedia (second-level domain) – is (subdomain) – wiki – Train, ie before the first “/” is read from right to left, and then the rest is read left to right.

For a more extensive discussion of HTTP URL and use, see above.

URL Overview

The term URL is also used outside the context of the World Wide Web. The database servers specified URL as a parameter to make connections to them. Similarly, any client-server application that follows a particular protocol can specify a URL format as part of its communication process.

Example of a URL in a database:

jdbc: DataDirect: oracle: / / myserver: 1521, sid = testdb

If a site is as unique and more or less permanently defined by a URL, it may be linked. This is not always the case, e.g., a menu option you can change the contents of a frame within the page without this new combination has its own URL.

A website may also depend on information stored temporarily. If the frame or website has its own URL, this is not always obvious to someone who wants to link to it: the URL of a frame does not appear in the browser address bar, and a page without address bar could have been produced. The URL can be found in the source code or “properties” of various components of the page.

Apart from the purpose of linking to a page or a page component, you may find you want to know the URL to show only the component, or overcome constraints such as a browser window that has no toolbars or is small in size and not adjustable.

Web servers also have the ability if the target URL has changed, allowing sites to change their structure without affecting existing links. This process is called URL forwarding.

Study: From Wikipedia, the free encyclopedia. The text is available under the Creative Commons.

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