16_WWW_WebForms1a_f08 - The World Wide Web Web-based...

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1 The World Wide Web: Web-based Applications and Web Forms Introduction to the World Wide Web and HTML • HTML: HyperText Markup Language – Language used to specify hypertext document content and how it is to be displayed • Hypertext – Non-sequential reading and writing – Text contains embedded hot words that are links to other documents – Hypermedia • Links can be references to non-textual information • Most recently, XHTML: Extensible Hypertext Markup Language
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2 World Wide Web (WWW) • Created at CERN (Switzerland high energy physics lab) by Tim Berners-Lee (1991) • Hypertext-based system for finding and accessing internet resources • Huge set of hypertext-linked documents on many computers WWW Important Acronyms • URL (Uniform Resource Locator) – The web “address” of a document (page) • HTTP (HyperText Transfer Protocol) – Protocol that specifies how a document is transferred • Defines how web browsers and web servers communicate with each other over a TCP/IP connection
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3 URL Format access protocol //: domain address / directory path / filename (type of object) (computer) (virt. directory) (file name) • Example: – http://cs.binghamton.edu/~reckert/360/topics.html Web Applications, Web Servers and Web Browsers • Windows applications (Windows Forms) run on one computer • Web applications require two programs – Usually run on two different computers connected over the internet • Web Server – Program that provides web documents (pages) to client applications running on other machines on the Internet – Pages are stored on the Web Server computer • Web Browser – Client program that interprets the HTML of a page provided by a Web Server and displays it • Common ones: Internet Explorer, Netscape Navigator, Mozilla FireFox • Pages may also contain programming logic in the form of a script that’s executed on the client machine (VBScript, JavaScript, etc.)
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4 Brief Introduction to JavaScript • Not a true programming language • Only works in a web browser • How it works: – Browser loads the page – Detects JavaScript <script> tag – Passes the script to the JavaScript Interpreter – Interpreter evaluates and performs the script – Interpreter passes HTML back to Browser – Browser displays the page • Note that this is client-side processing What Happens when a Web Page is Started • When user starts a web page, the browser sends an HTTP request to the Server • Server responds by sending the page – May be a preformatted HTML file – Or the program running on the Server may dynamically generate the HTML • This is server side processing • A request to view a Web page requires a round trip to server that stores the page
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Web Servers and Browsers A Simple HTTP Transaction (1) Client interacting with Web server. Step 1: The
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This note was uploaded on 12/04/2009 for the course ER CS 360 taught by Professor Reckert during the Spring '09 term at Istanbul Technical University.

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16_WWW_WebForms1a_f08 - The World Wide Web Web-based...

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