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How the World Wide Web works

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Presentation on theme: "How the World Wide Web works"— Presentation transcript:

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

2 History of the Web (1969) start of ARPAnet
(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

3 IP-adressing & DNS (domain name servers)
INTERNET SURFNET admin nl-domain: DNS aliasing ITC router admin ITC- domain: NVK server =

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

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 Standard configuration
GET file.gif GET file.html PUT file.gif PUT file.html <img src = “file.gif”> <br> <i>STATIC </i> MAP file.gif /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 Plugins (client-side)
PDF-READER <img src = “file.pdf”> <br><i> interactive </i> map file.pdf interactive map

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

10 JavaScript (client-side)
Java Virtual Machine <script > <!-- Document.write(“map”); } //--> </script> map map.", "width": "800" }

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

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

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

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

15 Internal server (itcnt07 student sites)
Only available within ITC (within “firewall”) administrator special dir “www” on personal drive M: authors windows network IIS server Web-browsers Anonymous access (Web) http

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

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