Simon Garcia

World Wide Web

The World Wide Web, literally the "web (spider) World," commonly called the Web, sometimes the Web or WWW is a hypertext system operating on public Internet and to view with a browser, pages put online sites. The image of the painting has hyperlinks that link web pages together.

The Web is an Internet applications. Other applications of the Internet are electronic mail, instant messaging, Usenet, etc.. The Web was invented several years after the Internet, but he has made the mainstream media attention to the Internet. Since then, the Web is often confused with the Internet, in particular, the word Web is often used in non-technical with no means clear whether the Web or Internet.

Terms designating the World Wide Web

The World Wide Web is and has been designated by many names and abbreviations synonyms: WorldWideWeb, World Wide Web, World-wide Web, Web, WWW, W3, World Wide Web, World Wide Web, Web.

The name of the original plan was WorldWideWeb. The words were quickly separated in World Wide Web to improve readability. The name World-Wide Web has also been used by the inventors of the Web, but the name now advocated by the World Wide Web Consortium between the three words without a hyphen. While "global" be written world-wide or worldwide in English, spelling and World Wide Web site are the abbreviation now well established.

By inventing the Web, Tim Berners-Lee had also thought about other names, such as Information Mesh (mesh of information), Mine of Information and The Information Mine (the mine of information, whose acronym is Tim).

The acronym WWW has been widely used to shorten World Wide Web before the Web abbreviation takes precedence. Pronunciation laborious in french and english WWW undoubtedly precipitate its decline. WWW is often pronounced three double V wéwéwé or vévévé.

The letters www still widely used in web addresses and some other uses formal or technical, though it responds to any technical constraint. In the second half of the 1990s, when networks were clogged by the growing popularity of the Web, a popular joke claimed that meant WWW World Wide Wait, is "waiting world." WWW is sometimes abbreviated as W3, abbreviation found in the symbol of the W3C World Wide Web Consortium.

Terms related to Web

The terminology of the Web contains several tens of terms. This chapter outlines those used in this article.

The term online means "connected to a network, namely the Internet computer network. This expression is not unique to the Web, is found on the phone.

A host is a computer online. Each Internet host is identified by an IP address which correspond to zero, one or more host names. This terminology is not unique to the Web, but to the Internet.

A resource on the World Wide Web is a computer (text, image, Usenet forum, mailbox, etc..) Regardless of other available resources. A resource in public access is freely accessible from the Internet. A local resource is present on the computer, as opposed to a remote resource (or online), available through a network.

You can not access a resource in maintaining a remote communication protocol. The functionality of each protocol varies: receiving, sending, and even exchange of information.

HTTP (for HyperText Transfer Protocol) is the communication protocol commonly used to transfer resources from the Web. HTTPS is the secure variant of this protocol.

A URL (for Uniform Resource Locator) pointing to a resource. It is a string to specify a communication protocol and a resource for the Web.

A hyperlink (or link) is an element in a resource associated with a URL. Web links are directed: they are able to go from one source to a destination. Only the resource to the source contains the data defining the hyperlink, the destination resource does bears no trace. There are two types of hyperlinks: those of the first type must be enabled to reach the destination in the second cause automatic access to the destination.

HTML (for HyperText Markup Language) is a computer language for describing the contents of a document (titles, paragraphs, layout of images, etc..) And include hyperlinks. An HTML document is a document described in HTML. HTML documents are the most viewed Web. HTML is now replaced by XHTML (Extensible HyperText Markup Language).

In a mode of communication client-server, a server is a host that runs a server which can connect the client software running on client hosts.

A web server is a host that runs an HTTP server (or web server). A web server hosting the resources it serves.

A web browser is an HTTP client software designed to access resources on the Web. Its basic function is to provide access to the HTML documents on HTTP servers. Support for other types of resource and other communication protocols depends on the browser in question.

A web page (or page) is designed to be viewed using a web browser. A web page is still divided into a central resource (usually an HTML document) and any resources accessed automatically (typically images).

An HTML editor (or publisher Web) is a software designed to facilitate the writing of HTML documents and web pages in general.

A website (or site) is a set of web pages and any other resources, linked in a coherent structure, issued by an owner (a business, government, association, individual, etc.). And hosted on a or more Web servers.

Visit a web site means "consult its pages. The term visit is that we usually consult several pages of a site visit as parts of a building. The visit is conducted by a user (or visitor or user). Audience measurement is obtained by copying the javascript code in a link to the site of a specialist service provider following the technique of marker distance.

A web address URL is a web page, usually written in a simplified form limited to a hostname. A website address is the address of a page of the site planned to accommodate visitors.

A web host is a host of services (bringing online) on its web servers resources constituting the websites of its customers.

An agency is a web services company creating websites for its customers.

The term surfing the Web means "consult the Web. It has been coined to emphasize the view that the Web is to follow many links from page to page. It is mainly used by the media, it is not the technical vocabulary.

A web directory is a website listing websites.

A web portal is a website trying to combine the widest range of information and services available in a website. Some are thematic portals.

A web service is a client-server technology based on Web protocols.

Exploring the deep Web and Web

The exploration of recursive Web from well-chosen resources is the basic method programmed into the crawlers of search engines. In 2004, the search engines to index about 4 billion of resources.

Deep Web or Invisible Web is the part of the Web is not indexed and therefore not found with general search engines. Studies indicate that the invisible Web is more than 99% of the Web [6]. The deep Web includes the following:

* Resources inaccessible to the public, so the robots, including substantive or administrative fee, protected by a password;
* The resources that are not provided by communication protocols supported by the robots (often only supports HTTP and HTTPS);
* Resources whose data format is not supported by the robot (only the HTML format is still supported);
* The resources listed in a file exclusion of robots;
* The resources excluded by the robot because they are designed to abuse the referencing (spamdexing);
* The resources excluded by the robot because they are deemed too inappropriate (eg if a site contains millions of resources that are not linked by any other site);
* The resources to which links are created dynamically in response to questions from visitors.

The latter resources are generally the databases and constitute the largest part of the deep Web.

Resource Types

The various types of Web resources have quite distinct uses:

* The resources constituting the web pages: HTML, JPEG or PNG or GIF, JavaScript, CSS, sounds, animations;
* Resources accessible from a web page but consulted with a specific interface: streaming audio, streaming video;
* The resources designed to be viewed separately: documents (PDF, PostScript, Word, etc..), Text file, pictures of all kinds, music, video, files to back up;
* The resources belonging to distinct systems Web: Usenet newsgroups, electronic mailboxes, local files.

HTML Documents

The HTML document is the main resource of a web page that contains hyperlinks, which contains the text and structure, which provides links and multimedia resources. An HTML document contains only text: the text consulted the text in HTML more than any other scripting or style.

The presentation of HTML documents is the main functionality of a web browser. HTML browser leaves the task to exploit the capabilities of the computer to present resources. Typically, the font, the length of lines of text, colors, etc., must be adapted to the output device (screen, printer, etc.).

Multimedia

The media elements to come resources independent of the HTML document. HTML documents contain links pointing to multimedia resources, which can be spread on the Internet. The multimedia elements are linked automatically to present a web page.

Only the use of images and small animations is standardized. The support of audio, video, three-dimensional spaces or other multimedia elements is still based on standardized technologies. Many browsers offer the possibility of transplanting software (plugin) to extend their functionality, including support for media types not standard.

Flows (audio, video) require a communication protocol different from the HTTP operation. This is one reason why this type of resource often requires a plugin and is not well integrated with web pages.

Images

This chapter deals with the images embedded in web pages.

The use of JPEG data format is suitable for natural images, mainly photographs.

The use of the PNG data format is indicated for the synthetic images (logos, graphics). It is also suitable for natural images, but only when the premium quality fully on the duration of the transfer.

The use of GIF data format is used for small animations. For synthetic images, the popular former GIF is often preferred to PNG. However, GIF has some disadvantages, including limiting the number of colors and a degree of compression is generally lower. Further controversy has surrounded the use of GIF from 1994 to 2004 because Unisys argued a patent covering the method of compression.

The use of images of XBM data format is obsolete.

Scripts

A scripting language used to write the text of a program run directly by software. Under the Web, a script is executed by a web browser program and actions meeting the use that the visitor makes the web page accessed. A script can be embedded in HTML document or from a resource bound. The first scripting language JavaScript Web was developed by Netscape. Then Microsoft developed a variant competitor as JScript. Finally, the ECMAScript standard has been proposed for the syntax and DOM standards for the interface with the documents.

Styles

The CSS was developed to manage in detail the presentation of HTML documents. The text in CSS can be integrated with the HTML document or from resources linked style sheets. This separation allows separate management of information (contained in HTML documents) and presentation (contained in Cascading Style Sheets). We also speak of "separation of content and form."

Other

The management of other types of resource depends on the software installed on the client host and their settings.

When the software is available, documents and images of all types are generally presented automatically, according to modalities (windows, dialogs) depending on the browser software and operating the type. If the type of resource is not managed, it is usually possible to save in a local file.

To manage the resources of various Web systems such as email, browsers usually use separate software. If a software does a resource type, a simple error message indicates.

XHTML is a markup language used to write pages for the World Wide Web. Originally designed as the successor of HTML, XHTML is based on the XML syntax defined by more recent, but more demanding than that defined by SGML is HTML that it is indeed to present a non-displayable content only by conventional computers, but also without too much degradation of the less powerful PDA.

The name XHTML

Like many languages based on XML, it begins with the letter X, which is the word eXtensible. So the first document describing officially called XHTML XHTML ™ 1.0 The Extensible HyperText Markup Language [1] ( "XHTML 1.0 The Extensible HyperText Markup Language). It is however the abbreviation XHTML is a trademark [2] World Wide Web Consortium (W3C) and is only used in the specification since version 1.0.

Cascading Style Sheets

CSS (Cascading Style Sheets: Cascading Style Sheets) is a computer language used to describe the presentation of HTML and XML documents. CSS defining standards are published by the World Wide Web Consortium (W3C). Introduced in mid 1990, CSS is commonly used in web design and well supported by web browsers in the 2000s.

Allow the cascade of styles

The "cascade" is the combination of different sources of styles applied to the same document, depending on their respective level of priority. Different modes of cascade can be combined:

* Origin of styles, from the user agent, the author and the user. The higher priority given to styles of the user is a major contributor to accessibility of documents with CSS.
* By media: a generic style sheet may apply to several media restitution (screen display, printing, projection) and be combined with leaves of each media.
* According to the architecture of a set of web documents: a generic stylesheet can be applied to all pages of a website, be combined with leaves of each section thereof, as with styles unique to a particular page.
* According to the architecture of the leaves themselves: an external style sheet to the document can be combined with a stylesheet internally and styles directly applied to each element which composes (styles online). A stylesheet can also import one or more other outer leaves.

Accessibility

CSS promotes accessibility of a web page providing the ultimate in user control rendering of a document in their browser: it is possible to adapt to constraints or preferences concerning eg display size of characters or colors. By separating structure and presentation, CSS promotes writing structured documents in a semantic potentially exploitable by technical aids: the freedom of the elements of titration can be used to adhere strictly to the formal hierarchy of these , which in turn aid techniques to establish a table of contents waterway. Finally, by giving authors the means to enrich the text formatting, CSS allows you to limit the use of texts in images [46].

However, certain uses of CSS may also jeopardize the accessibility of content:

* By replacing the latter pseudo-content that are available only to users who can perceive visual CSS rendering: for instance information to be conveyed by images of the background.
* In moving the necessary consistency between the linear order of information in the content structure and visual rendering CSS displayed. Technical aids such as screen readers did in fact access to this linear order: information that would make sense in terms of its positioning CSS is not understandable to their users.
* In an accessibility based on the relevance of the HTML structure, the range of options for formatting content with CSS can lose sight of the need to tag the content using meaningful elements. For example, it is possible to define a quote visually by putting in italics or in the surrounding quotes, but information on the origin of this text will be visible to the standards of accessibility, via the use q or blockquote elements, which are only used to define a summons and HTML to indicate the source via the appropriate attribute (cite).

Methods of implementation guidelines for web content accessibility (RGAA, UWEM for example) thus define the rules of practice styles CSS [47].

Simplicity

CSS responds to a desire for a simple presentation format, both in its features in its syntax, in order to facilitate the direct manipulation of the authors and users. However, this simplicity is affected by several factors:

* Difficulty in identifying and controlling the outcome of the cascade when the sources of styles abound. The final rendering of content depends on the precise combination of several sheets and may then become difficult to change. The interdependence of style sheets can make it difficult to anticipate the result of a change to one of them. The authors are faced with a choice between this interdependence that optimizes the amount of code redundancy and styles that facilitates its maintenance [48].
* The difficulty writing styles of users without advanced skills. Users are in theory the primary beneficiaries of CSS, which gives them the opportunity to tailor the presentation of web pages. However, the mechanism of styles is difficult to develop a graphical environment that would facilitate the handling of CSS properties [49]. In practice, the use of user styles, therefore, remains marginal.

Dynamic HTML

Dynamic HTML, English, Dynamic HTML, DHTML often abbreviated, is a generic name given to all the techniques used by the author of a web page so that it is able to change itself being consultation in the web browser. This name was particularly popular in the late 1990s when these techniques have emerged. They are now commonly used not as advertised.

Technique

Technically, the changes relate to the internal representation that the browser made the web page. The browser immediately reflects those changes on the screen. The components of the page may be modified, moved, created or deleted, or automatically in response to a visitor. Seizures in the form fields can also be controlled. In addition, a rapid succession of changes of properties of certain elements (color, size, position, etc..) Can be used to create an animation.

The internal representation is initially determined by the HTML document and CSS style information constituting the web page. The changes are described with a computer scripting language like JavaScript, which accesses the internal representation through the programming interface Document Object Model (DOM).

JavaScript

JavaScript is a scripting language mainly used in web pages interactive. It is an object oriented language to prototype, ie that the basis of language and its key interfaces are provided by objects that are not instances of classes, but which are each equipped with manufacturers to generate their properties, including a prototype property which allows to generate custom objects heirs.

Adobe Flash

Adobe Flash (formerly Macromedia Flash Animator FutureSplash original name), or simply Flash, refers to Adobe Flash Player and a multimedia software used to create content Adobe Engagement Platform (such as an Internet application, games or movies). Flash Player, developed and distributed by Adobe Systems (which bought Macromedia in 2005), is a client application running on most Web browsers. This software allows the creation of vector graphics and bitmap, a scripting language called ActionScript and bi-directional stream of audio and video.

In short, Adobe Flash is a software integrated development environment (IDE), a virtual machine used by a server or Flash player to view flash files Flash. But the term "Flash" can refer to a reader, an environment or an application file.

Since its launch in 1996, Flash technology has become one of the most popular methods to add animations and interactive objects to a web page, and many creation software and OS are able to create or display Flash. Flash is commonly used to create animations, advertisements and video games. It can also incorporate video streaming in a page, until the development of Rich Media applications.

Flash files, usually called "Flash" are in. Swf. They may be included in a web page and read by the Flash browser plugin, or read independently in the Flash Player.

Uses

Flash files can be created in a web page for use on the Internet or can be shown as independent (in the form of a single executable file, without plug) for use offline. The graphical content of Flash files can get rich web applications thanks to the support vector and multimedia files that include digital sound and digital video. Flash is used to produce visual content in the so-called "rich" and "Motion Design" Web.

This software is currently used in the following contexts:

* Creation of Internet sites and video games distributed on the World Wide Web.
* Creation of illustrations.
* Making Movies for television or cinema (generic, music videos, commercials, short films of animation).
* Designed to dress for television.
* Creation of multimedia applications.
* Portions interfaces video games
* Create slideshows interactive.
* Creation of advertising banners.
* Distributions marketing CDs.
* Dissemination of videos over the Web.
* Web module to interact with a database.
* Flash Video extension. Flv

Photoshop

Photoshop is an editing, processing and computer assisted drafting published by Adobe. It is primarily used for processing digital photographs, but also serves to create images ex nihilo.

Photoshop is a program working on raster images (also called "bitmap", not to be confused with the recording format Windows bitmap), because the images are made up of a grid of points called pixels. The interest of these images is to reproduce subtle gradations of color.

Recognized by the computer graphics professionals through its powerful gallery of filters and graphics tools, it is now taught in larger schools, institutes of Fine Arts and used by a large majority of studios and creative agencies.

Web design

In French, the term web design is often used against the meaning of its English meaning and confused with the only graphic design. But that is not defined as the visual expression and / or artistic, that the formalization of constraints for the creation, marketing and technical constraints.

Web design means the design of the web interface: the interactional architecture, the organization of pages, the navigation tree and a website. It is an essential phase in the design of such a site. Designing a web design takes into account the constraints of the Internet in terms of ergonomics, usability and accessibility.

Web design therefore calls for a variety of skills: coding, interactivity and ergonomics, and good knowledge of the technical constraints associated with this field: respect for W3C recommendations, accessibility, portability.

The design of a site is presented as a model functional and technical specifications. These are then processed with the model graphically, lines of code and images to be displayed in a web browser.