Overview of WWW Web Pages Web Sites Web

Overview of WWW, Web Pages, Web Sites, Web Application, Web Servers and HTTP

WORLD WIDE WEB (WWW) The World Wide Web is a way of exchanging information between computers on the Internet. The World Wide Web is the network of pages of images, texts and sounds on the Internet which can be viewed using browser software.

WWW Structure Clients use browser application to send URIs via HTTP to servers requesting a Web pages constructed using HTML (or other markup language) and consist of text, graphics, sounds plus embedded files Servers (or caches) respond with requested Web page Or with error message Client’s browser renders Web page returned by server Page is written using Hyper Text Markup Language (HTML) Displaying text, graphics and sound in browser Writing data as well The entire system runs over standard networking protocols (TCP/IP, DNS, …)

WWW COMPONENTS Structural Components Clients/browsers – to dominant implementations Servers – run on sophisticated hardware Caches – many interesting implementations Internet – the global infrastructure which facilitates data transfer Semantic Components Hyper Text Transfer Protocol (HTTP) Hyper Text Markup Language (HTML) – extensible Markup Language (XML) Uniform Resource Identifiers (URIs)

Fundamental concept of the WWW Hypertext is text which contains links to other texts. Hypermedia is a term used for hypertext which is not constrained to be text: it can include graphics, video and sound.

Continue…. WEB Browser A web browser displays a web document and enables users to access web documents. WEB Server This is a program that waits patiently for the browser to request a web page. The servers looks for the requested information, retrieves it and send it to the browser or sends an error message if the file is not found. Uniform Resource Locator (URL) These are the web addresses. The resource locator is an addressing system.

Web Pages A Web page is a document for the World Wide Web that is identified by a unique uniform resource locator (URL). A Web page can be accessed and displayed on a monitor or mobile device through a Web browser. The data found in a Web page is usually in HTML format. The Web pages usually also contain other resources such as style sheets, scripts and images for presentation. Users may be able to navigate to other pages through hypertext links.

Web Sites A website is a set of related web pages typically served from a single web domain. A website is a collection of Web pages, images, videos or other digital assets that is hosted on one or more web servers, usually accessible via the internet. The pages of a website can usually be accessed from a common root URL called the homepage and usually reside on the same physical server.

Web Application A web application or web app, short for web-based application, is software that runs in an Internet browser. Similar to desktop computer software or a mobile app, a web application provides a user interface, offers utility or entertainment, and the ability to access, create, store, or modify data.

Web Servers Web server is a computer where the web content is stored. Basically web server is used to host the web sites but there exists other web servers also such as gaming, storage, FTP, email etc.

HTTP & HTTPS HTTP means Hypertext Transfer Protocol. HTTP is the underlying protocol used by the World Wide Web and this protocol defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands. For example, when you enter a URL in your browser, this actually sends an HTTP command to the Web server directing it to fetch and transmit the requested Web page. The other main standard that controls how the World Wide Web works is HTML, which covers how Web pages are formatted and displayed. HTTP is called a stateless protocol because each command is executed independently, without any knowledge of the commands that came before it. This is the main reason that it is difficult to implement Web sites that react intelligently to user input. HTTPS: A similar abbreviation, HTTPS means Hyper Text Transfer Protocol Secure. Basically, it is the secure version of HTTP. Communications between the browser and website are encrypted by Transport Layer Security (TLS), or its predecessor, Secure Sockets Layer (SSL).