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  1. 1. URL
  2. 2. <ul><li>There were three question that had to be answered before a selected page could be displayed: </li></ul><ul><ul><ul><ul><ul><li>What is the page called? </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Where is the page located? </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>How can the page be accessed? </li></ul></ul></ul></ul></ul>
  3. 3. <ul><li>Each page is assigned a URL (Uniform Resource Locator) that effectively serves as the page’s worldwide name. </li></ul><ul><li>URL is like a sign pointing to something on the internet service tell that what type of internet service to use. </li></ul>
  4. 4. <ul><li>URL have three part: </li></ul><ul><li>how_to_get_there://where_to_go/what_to _get </li></ul><ul><ul><ul><ul><li>the protocol </li></ul></ul></ul></ul><ul><ul><ul><ul><li>The DNS name of the host </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Local name uniquely indicating the specific page </li></ul></ul></ul></ul>
  5. 5. For example… <ul><li>http://www.cs.vu.nl/welcome.html </li></ul><ul><li>protocol is http </li></ul><ul><li>DNS name of the host www.cs.vu.nl </li></ul><ul><li>file name is welcome.html </li></ul>
  6. 6. <ul><li>URL scheme is open-ended in the sense that it is straight forward to have protocol other than HTTP </li></ul>
  7. 7. telnet://www.w3.org:80 Remote login telnet mailto Sending email mailto Gopher://gopher.tc.umn.edu/11/libraries Gopher Gopher News:comp.os.minix News group News /user/suzanne/prog.c Local file File ftp://ftp.cs.vu.nl/pub/minix/README FTP ftp http://www.cs.vu.nl/ast/ Hypertext http Example Used for Name
  8. 8. LOCATING INFORMATION IN WEB <ul><li>The web contain wast amout of information,finding the right item is not so easy. </li></ul><ul><li>Programs that search the web are sometimes called search engines,spiders,crawlers,worms,orknowbots. </li></ul>
  9. 10. pointer to URLS Pointers to title String storage 0 1 2 3 2 0 1 2 3 4 5 19 6 21 44 Hash code Overflow chains url_table heap Hash table
  10. 11. HTML
  11. 12. What it is… <ul><li>HTML is an application of ISO standard 8879,specialized to hypertext and adapted to the web. </li></ul><ul><li>Very structured markup language for building web pages. </li></ul><ul><li>A markup language is a collection of elements, which are used to indicate structure and format of a document </li></ul><ul><li>Browser simply has to understand the markup commands </li></ul>
  12. 13. HTML standards <ul><li>When Mosaic was the only browser, the language it interpreted,HTML 1.0,was the de facto standard. </li></ul><ul><li>When new browser came along, there was a need for a formal standard, so HTML2.0 standard was produced. </li></ul><ul><li>HTML3.0 was initially created as a reserch effort to add many features to HTML2.0,including tables,toolbars,mathematical formulas, advanced stylesheets,and more </li></ul>
  13. 14. <ul><li>A complete html element is defined by a start tag, an end tag, possible attributes and a content model </li></ul><ul><li>The commands inside the tags are called directives </li></ul>
  14. 15. <ul><li>A proper web page consists of a head and a body enclosed by <HTML>and</HTML> tag. </li></ul>
  15. 16. Common HTML tags Brackets a menu of<LI>items <MENU>…</MENU> Brackets a numbered list <OL>…</OL> Brackets an unordered <UL>…</UL> Set…in italics <l>…</l> Set…in boldface <B>…</B> Delimits a level n heading <Hn>…</Hn> Delimits the page’s body <body>…</body> Defines the title <title>…</title> Delimits the page’s head <HEAD>…</HEAD> Declares the web page to be written in HTML <HTML>…</HTML> Description Tag
  16. 17. Define a hyper link <A HRFE=“…”>…</A> Load an image here <IMG SRC=“ ...”> Preformatted text; do not reformat <PRE>…</PRE> Horizontal rule <HR> Start of paragraph <p> Force a break here <BR> Start of a list item <LI> Description Tag
  17. 18. Forms <ul><li>Forms contain boxes or buttons that allow users to fill in information or make choices and then send the information back to the page’s owner. </li></ul><ul><li>Using the <INPUT> tag for this purpose. </li></ul><ul><li>Most common forms are blank fields for accepting user text, boxes that can be checked, active maps, and submit buttons. </li></ul>
  18. 19. <ul><li>Thank you </li></ul>