World Wide Web | Part 3
Other Types Of Web Resources
The management of other types of resource depends on the software installed on the client host and their settings.
When the corresponding software is available, documents and pictures of all types are usually automatically presented in a way (windows, dialogs) depending on the browser software and operating the type. When the type of resource is not managed, it is usually possible to save a local file.
To manage the resources of various Web systems such as email, browsers usually involve separate software. If no software manages a resource type, a simple error message indicates.
Design
The Web was designed to be accessible with the computer equipment the most diverse workstation computer terminal in text mode, personal computer, PDA, etc. This universal access depends primarily on the universality of Internet protocols. Secondly, it depends on the flexibility of presentation of Web pages, offered by HTML. In addition, HTTP provides boaters the opportunity to negotiate the type of each resource. Finally, CSS can offer different presentations, selected for their consistency with the equipment used.
The W3C was created for that standard in order to allow the independence of tools used to create content with those who used to read it. This is called interoperability.
Web accessibility for individuals with disabilities is also the subject of special attention as the Web Accessibility Initiative.
Decentralization
Web technologies impose no organization between web pages, let alone between websites. Any Web page can contain hyperlinks to other resources available on the Internet. Establishing a link requires absolutely no action on the side of the resource pointed. There is no centralized registry of hyperlinks to pages or sites. The only register used is that the DNS is a distributed database that lists hosts and is useful for all Internet-based systems.
This decentralized design should encourage, and has promoted a rapid increase in the size of the Web. She also encouraged the development of sites specialize in information on other sites: directories and search engines. Without these sites looking for information on the Web would be extremely laborious. The opposite approach, the Web portal, means trying to concentrate as much information and services in one location.
A weakness of decentralization is the lack of monitoring when a resource is moved or deleted the links that the pointed end up broken. And this is visible in activating the hyperlink, where the most common result is the error message 404.
Technology
Pre-existing technology
The Web is based on Internet technologies, including TCP / IP to transfer data to convert the DNS host names to IP addresses and to indicate the MIME type of data. The standard character encoding and digital image formats GIF and JPEG have been developed independently.
Three technologies have been developed for the World Wide Web:
- URLs in order to identify any resource in a hyperlink;
- HTML to write web pages containing hyperlinks;
- The HTTP communication protocol used between browsers and Web servers, which can specify the MIME type of resources transferred.
These technologies were first standardized as other Internet technologies: using the process of Request for Comments. This gave the RFC 1738 for the URL, RFC 1866 HTML 2.0 and RFC 1945 for HTTP/1.0.
The World Wide Web Consortium (W3C) was founded in 1994 to develop and promote the new web standards. Its particular role is to ensure the universality of new technologies. Technologies have been developed by private companies.
Current Web Technology
Major current standards are:
- XML 1.0 developed to provide markup languages, including HTML, syntax simpler than SGML;
- HTML 4.01 based on SGML, and XHTML based on XML 1.0;
- RFC 2396 (Uniform Resource Identifiers), which includes the URL;
- RFC 2616 (HTTP/1.1);
- Stylesheets cascading CSS level 1 and level 2;
- The DOM document model level 1 and level 2;
- The JavaScript scripting language for manipulating documents;
- The digital image formats PNG, JPEG and GIF.
Server Technologies
In addition to the communication protocols and formats of data exchanged on the Web, several techniques to the Web are used to run Web servers. As these techniques do not leave the server, they are not standardized by the World Wide Web Consortium.
- The standard CGI (Common Gateway Interface) is a protocol for inter-process communication between the HTTP server and external applications.
- The programming language PHP (PHP: Hypertext Preprocessor) was developed to generate web pages. It has strong integration with the HTTP and HTML.
- The engine ASP (Active Server Pages) has been developed by Microsoft to interpret the script language in IIS (Internet Information Services).
Study: From Wikipedia, the free encyclopedia. The text is available under the Creative Commons.
