2. Chapter 16: The World Wide Web Chapter 16 The World Wide Web Page 189 Click on this piece of hypertext, and you’re taken to... Type in a keyword and click the “Go!” pushbutton, and you’re taken to... Click on this pushbutton, and you’re taken to... The World Wide Web applies point-and- click hypermedia application software to facilitate accessing documents on the Internet via TCP-based protocols. And with additional downloaded software, elaborate Web sites that include more than text and simple images can be accessed.

3. Chapter 16 The World Wide Web Page 190 H yper T ext T ransport P rotocol (HTTP) Welcome to IEEExpl <img src="/images/subidinfmast_01.gif" width="550" height="39“ vspace="3" hspace="0" border="0" alt="IEEE xpl Subscription Access Information“ usemap="#Map"> Your institution subscribes to: <font face=Verdana, Arial, Helvetica, sans-serif size=2 color=#3333CC>• Search Xplore Database Your institution subscribes to: • IEEE All Society Periodicals Package (ASPP) Your online subscription includes access to the abstracts and full-text of IEEE journals, transactions, and magazines published since 1998: <font face=Verdana, Arial, Helvetica, sans-serif size=2 color=#3333CC> • IEEE journals, transactions, and magazines In addtion to the above, you may purchase individual IEEE journal/magazine articles and conference papers that are not included in your institution's online subscription. If you want a copy of an article or paper, first check with your librarian for a copy available locally. Any questions? Contact IEEE Customer Service. Welcome to IEEExpl <img src="/images/subidinfmast_01.gif" width="550" height="39“ vspace="3" hspace="0" border="0" alt="IEEE xpl Subscription Access Information“ usemap="#Map"> Your institution subscribes to: <font face=Verdana, Arial, Helvetica, sans-serif size=2 color=#3333CC>• Search Xplore Database Your institution subscribes to: • IEEE All Society Periodicals Package (ASPP) Your online subscription includes access to the abstracts and full-text of IEEE journals, transactions, and magazines published since 1998: <font face=Verdana, Arial, Helvetica, sans-serif size=2 color=#3333CC> • IEEE journals, transactions, and magazines In addtion to the above, you may purchase individual IEEE journal/magazine articles and conference papers that are not included in your institution's online subscription. If you want a copy of an article or paper, first check with your librarian for a copy available locally. Any questions? Contact IEEE Customer Service. HTTP is the software defining the format of requests relayed from a Web browser to a Web server, as well as the replies relayed from the server to the browser. HTML (HyperText Markup Language) is the standard used to write Web pages; it doesn’t require specific formatting instructions, so two browsers may display a page differently.

4. Chapter 16 The World Wide Web Page 191 Extensible Markup Language (XML) Unlike HTML, XML allows users to include content-specific information in their files, facilitating its being formatted to suit various display devices. A job vacancy at the department of Tourism is added to the job database. XML technology stores the data separately from the presentation, allowing for a variety of platforms. The vacancy is displayed on the job center kiosk......can be accessed by mobile devices......and is displayed on the Department of Tourism website.

5. Chapter 16 The World Wide Web Page 192 Uniform Resource Locators (URLs) A URL specifies three pieces of information: 1. Type of file transfer 1. Type of file transfer 2. Name of computer 2. Name of computer 3. Name of file 3. Name of file For example: http://www.cs.siue.edu/undergrad/BS/files/prerequisites.pdf http://www.cs.siue.edu/undergrad/BS/files/prerequisites.pdf 1. http:// - type of file transfer 1. http:// - type of file transfer 2. cs.siue.edu - name of the computer 2. cs.siue.edu - name of the computer 3. /undergrad/BS/files/prerequisites.pdf - location of the file on the computer 3. /undergrad/BS/files/prerequisites.pdf - location of the file on the computer Different types of file transfer: http:// - hypertext transfer protocol http:// - hypertext transfer protocol ftp:// - file transfer protocol ftp:// - file transfer protocol telnet:// - opens a telnet session telnet:// - opens a telnet session gopher:// - transfer file from a gopher server gopher:// - transfer file from a gopher server mailto:- open a mail session mailto:- open a mail session

6. Chapter 16 The World Wide Web Page 193 Network Interface HTTPClientHTTPClientFTPClientFTPClient BrowserController Client software running on the workstation BrowserController Client software running on the workstation JavaInterpreterJavaInterpreter HTMLInterpreterHTMLInterpreter Display Driver Issuing requests for external files Web Browsing Input from mouse & keyboard Communications with remote Web server Output to user’sdisplay Interpretingdownloaded Web pages and files

7. Chapter 16 The World Wide Web Page 194 Internet Search Engines Search engines use “spider” programs to “crawl” through the Web, building a list of words. Some follow every link on every home page. Some ignore links that lead to graphics, sound, or animation files, or to newsgroups. Some concentrate primarily on the most popular Web pages.

8. Chapter 16 The World Wide Web Page 195 Comparing Search Engines Security Issues Red = distribute adware, send a high volume of spam, or make unauthorized changes to a user's computer Yellow = send a high volume of "non- spammy" email, display many popup ads, or prompt a user to change browser settings Share of Searches