Chapter 1: Introduction to Web Kingdom of Saudi Arabia Ministry of Higher Education Al-Imam Mohammad Bin Saud Islamic University College of Computer and Information Sciences Chapter 1: Introduction to Web IS 203: Web Programming Information Systems Department

Information Systems Department Table of contents History of Web Web System Architecture URL DNS Protocols governing the Web HTTP Request Response Creating Static and Dynamic Websites Information Systems Department

Information Systems Department History of Web In the 1960's, Ted Nelson popularized the hypertext concept, and Douglas Engelbart created the first working hypertext systems. In 1989, Tim Berners-Lee had suggested a way to let all users, but particularly scientists, browse each others’ papers on the Internet. He developed HTML, URLs, and HTTP. Information Systems Department

Information Systems Department What is a Web ? The Web is a shared information space. Information Systems Department

Basic Web System Architecture The web is a two-tiered architecture. A web browser displays information content, and a web server that transfers information to the client. Information Systems Department

Information Systems Department Web Browser The primary purpose is to bring information resources to the user. An application for retrieving, presenting, and traversing information resources. Information Systems Department

History of Web Browsers

History of Web Browsers

History of Web Browsers

History of Web Browsers

History of Web Browsers

Information Systems Department Web Server The term web server or webserver can mean one of two things: A computer program that accepts HTTP requests and return HTTP responses with optional data content. A computer that runs a computer program as described above. Information Systems Department

Basic Web System Architecture This architecture depends on three key standards: HTML for encoding document content. URLs for naming remote information objects in a global namespace. HTTP for staging the transfer. Information Systems Department

HTML Hypertext Markup Language Document layout language (not a programming language) Defines structure and appearance of Web pages

URL Uniform Resource Locator URLs are location dependent It contains four distinct parts: the protocol type, the machine name, the directory path and the file name. There are several kinds of URLs: file URLs, FTP URLs, and HTTP URLs.

HTTP Hyper Text Transfer Protocol HTTP is a request/response standard of a client and a server. Typically, an HTTP client initiates a request. Resources to be accessed by HTTP Information Systems Department

Information Systems Department HTTP Request Methods HTTP defines eight methods (sometimes referred to as "verbs") indicating the desired action to be performed on the identified resource. HEAD GET POST PUT DELETE TRACE OPTIONS CONNECT Information Systems Department

Sample HTTP Request and Response Client request Server response Information Systems Department

Web Architecture Extension CGI extends the architecture to three-tiers by adding a back-end server that provides services to the Web server. Information Systems Department

Database Driven Website Architecture Information Systems Department

Server-side Processing In server-side processing, the Web server: Receives the dynamic Web page request Performs all of the processing necessary to create the dynamic Web page Sends the finished Web page to the client for display in the client’s browser Information Systems Department

Client-side Processing Some processing needs to be “executed” by the browser, either to form the request for the dynamic Web page or to create or display the dynamic Web page. Eg. Javascript code to validate user input Information Systems Department

Server and Client side processing Server-side processing PHP ASP ASP.NET Perl J2EE Python, e.g. Django Ruby, e.g. Ruby on Rails ColdFusion Client-side processing CSS HTML JavaScript Adobe Flex Microsoft Silverlight Information Systems Department

Information Systems Department Domain Name System DNS Each host on the Internet has a range of IP (or Internet protocol) numbers. The Domain name system (DNS) maps the numbers to names of hosts or websites (eg www.google.com, www.hotmail.com). Information Systems Department

Protocols Governing the Web TCP/IP, or Transmission Control Protocol-Internet Protocol. Essentially, TCP/IP describes a protocol which will work on any sort of computer and operating system for transportation of data across the internet between different systems.  SMTP, or the Simple Message Transfer Protocol, is the basic standard for email, and again exists since the 1980s when the Internet was small and honest. Another important protocol which dates from pre 1972 is FTP, or the file transfer protocol. This simply is the way to upload or download a file from an Internet computer. With the coming of the World Wide Web, we see another powerful protocol - http, or hypertext transfer protocol. HTTP allows us to click on the name of a site and visit it. Simple, but very powerful. Information Systems Department

Static vs Dynamic Sites A static web site is a web site where the content, the HTML and graphics, are always static—it is served up to any visitor the same, unless the person who created the web site decides to manually change the copy of it on the server. On a dynamic web site on the other hand, the content on the server is the same, but instead of just being HTML, it also contains dynamic code, which may display different data depending on information you feed to the web site. Another thing to note is that special software must be installed on the server to create a dynamic web site. Information Systems Department