How the World Wide Web works

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How the World Wide Web works

• Barend Köbben
• International Institute for Geo-information
  Science and Earth Observation (ITC)

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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

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IP-adressing DNS (domain name servers)
INTERNET
www.kartografie.nl
kartoweb.itc.nl
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HTTP communication

• Client-server architecture

Client
Server
Webserver (IIS, Netscape, HTTPd)
Browser (Explorer, Netscape, Opera)
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HTML code

• ltPgtHelloltBgtWorldlt/BgtltHRgtHow areltIgtyoult/Igt?ltPgtltA
  HREF otherfile.htmlgtClick herelt/agt to go.
• Looks like
• Hello World
• How are you?
• Click here to go.

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Standard configuration
http// www.itc.nl /file.html
STATIC MAP
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Constraints

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

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Plugins (client-side)
PDF-READER
interactive map
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Java applets (client-side)
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JavaScript (client-side)
ltscript gt lt!-- Document.write(map) //--gt lt/sc
riptgt
map
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CGIapplications (server-side)
www.kartografie.nl /CGI?makemaptitleitc
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Active Server Pages (server-side) handles
JavaScript or VBscript
Microsoft IIS
HTML
in memory
ltimg src map.gifgtltbrgtdatabase stuff
server-plugin(asp.dll)
a
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Java servlets (server-side)
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ArcView-IMS a mixed solution
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Internal server (itcnt07 student sites)

• Only available within ITC (within firewall)

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External Web server (eg. Kartoweb)