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How the World Wide Web works

How the World Wide Web works. Barend Köbben International Institute for Geo-information Science and Earth Observation (ITC). History of the Web. (1983) ARPAnet, USEnet en EUnet adopt TCP/IP communication: birth of the Internet many protocols run “on top of” TCP/IP (telnet, ftp, smpt)

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How the World Wide Web works

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  1. How the World Wide Web works Barend Köbben International Institute for Geo-information Science and Earth Observation (ITC)

  2. History of the Web • (1983) ARPAnet, USEnet en EUnet adopt TCP/IP communication: birth of the Internet • many protocols run “on top of” TCP/IP (telnet, ftp, smpt) • because of IP-adressing all networks can can be seen as one big network • (1991) definition of the WWW-protocols: • HTTP: HyperText Transfer Protocol • HTML: HyperText Markup Language (1969) start of ARPAnet

  3. DNS aliasing SURFNET admin nl-domain: xx.xx.nl ITC router admin ITC-domain: xx.itc.nl NVK server 192.92.92.70 IP-adressing & DNS (domain name servers) INTERNET www.kartografie.nl =kartoweb.itc.nl

  4. Can I have that file? Here it is... HTTP communication • Client-server architecture Client Server Webserver (IIS, Netscape, HTTPd) Browser (Explorer, Netscape, Opera)

  5. HTML code • <P>Hello<B>World</B><HR>How are<I>you</I>?<P><A HREF= ”otherfile.html”>Click here</a> to go. • Looks like: • Hello World • How are you? • Click here to go.

  6. PUT file.gif PUT file.html GET file.gif GET file.html file.gif <img src = “file.gif”><br><i>STATIC </i> MAP Standard configuration http:// www.itc.nl /file.html STATIC MAP

  7. Constraints • Standard configuration offers: • HTTP communication-protocol • HTML–, GIF– en JPEG–formats • Static maps only • No interactivity (except “clickable maps”) • Overcoming the constraints: • Only possible by adding data-formats and protocols • Possible loss of platform independency

  8. file.pdf <img src = “file.pdf”><br><i>interactive </i> map Plugins (client-side) PDF-READER interactive map

  9. Java Virtual Machine map.class Java-applet code map applet <applet src = “map.class”> <br> map applet Java applets (client-side)

  10. Java Virtual Machine JavaScript (client-side) <script > <!-- Document.write(“map”); } //--> </script> map

  11. CGI-APPLI-CATION itc CGI–applications (server-side) www.kartografie.nl /CGI?makemap&title=“itc”

  12. <img src = <% foundrecords.image %><br>database stuff database stuff Active Server Pages (server-side)handles JavaScript or VBscript Microsoft IIS HTML in memory <img src = map.gif><br>database stuff server-plugin(asp.dll) a

  13. Java Virtual Machine map.class Java-applet code map applet <%applet src = “map.class”%> <br> map applet Java servlets (server-side)

  14. server-plugin(esrimap.dll) Java Virtual Machine arcview map mapcafe.class Java-applet code ArcView-IMS: a mixed solution

  15. administrator(blenke@itc.nl) IIS serveritcnt07.itc.nl special dir “www” on personal drive M: windowsnetwork http Anonymous access (Web) Web-browsers authors Internal server (itcnt07 student sites) • Only available within ITC (within “firewall”)

  16. administrator(kartoweb@itc.nl) Kartoweb server ftp http username/password privileges Anonymous access (Web) Web-browsers authors External Web server (eg. Kartoweb)

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